Okay, so she was telling him to kiss her.
Ian wants to be sure this is okay:

“It won’t upset you? Melanie won’t bother you?”

Not “Melanie’s okay with it?” but “Melanie won’t bother you?” because Melanie’s feelings could not be more irrelevant to Ian. He doesn’t care why she isn’t causing trouble, or even if she’s an issue – if the brainslug’s just stopped being bothered hearing Melanie say to stop, that’s fine too.

He kisses her.

“No, Ian. Really kiss me. Like… like you’re trying to get slapped. Do you understand?”

No, I don’t. Your phrasing sounds like you think women slapping men is primarily tied to how sexy the kiss is and objecting is secondary if at all a real factor. If she’d said “like you’re trying to get slapped by Melanie” this would read properly, and it’d also describe what her plan presumably is.

Anyway, he wants to know what’s up, so she kisses him instead. Yay for actual initiative, I guess.

This wouldn’t have worked with another species. Another mind wouldn’t have been so easily overwhelmed by its body. Other species had their priorities in better order.

I’m pretty sure prioritizing reproduction is the better order, evolutionarily speaking.

It was just the two of us, so close that we hardly counted as two.

This is a terrible analogy to have a brainslug make. Kissing really hard can’t compare to inserting yourself into someone else’s body and manually hijacking their brain.

She explains she was doing all that to find Melanie.

How can I tell him that I’ve lost his sister now? Ian, he’s sick! I can’t tell him that! I’ll upset him, make it harder for him to get well.

Speaking of better priority order, it’d be nice if you actually gave a fuck about Melanie instead of claiming to be friends but only caring what happens to her to the degree the male characters might be unhappy.

“Oh, Ian! It was right after I saw… in the hospital. And she tried to defend them… and I screamed at her… and I–I made her go away! And I haven’t heard her since. I can’t find her!”

I’d also like to point out that for all the early claims that she’s strong, in the end she gets full control of the body by chance and accomplishes it during hysteria.

“Shh,” he said again. “Calmly. Okay. Now, what do you really want? I know you don’t want to upset Jamie, but he’s going to be fine regardless. So, consider–would it be better, just for you, if –”

Christ.

Anyway, no. She explains killing Melanie would be like how they killed those people – which is to say, she objects only in the general sense of not wanting to kill people, having no attachment to Melanie as a person.

Ian, being a dick-haver and therefore capable of smarter plans, remembers that he’s not the one Melanie had the strongest reaction to, so he’s the wrong kiss target. He goes to get Jared while she sits and pleads with Melanie to come back because Jamie needs her – which is frankly rather lucky since it’s growingly obvious that the brainslug would not be so upset otherwise.

So Jared gets there and actually expresses concern for his girlfriend and upset she’s gone, making him the only person alive who does.

He tried to kiss me softly. I could tell that he tried. But his intentions went up in smoke, just like
before.
There was fire everywhere, because he was everywhere. His hands traced my skin, burning it. His lips tasted every inch of my face. The rock wall slammed into my back, but there was no pain. I couldn’t feel anything besides the burning.
My hands knotted in his hair, pulling him to me as if there were any possible way for us to be closer. My legs wrapped around his waist, the wall giving me the leverage I needed. His tongue twisted with mine, and there was no part of my mind that was not invaded by the insane desire that possessed me.

I had to read it so you do too.

Anyway, while she’s just yay kissing, he’s actually thinking about Melanie and calls to her between kisses. She wakes up and

He pulled his mouth free and pre

Jared! Jared! NO!
I let her flow through my arms, knowing this was what I wanted, though I could barely pay attention now. The hands on his stomach turned hard, angry. The fingers clawed at his skin and then shoved him as hard as they could.
“NO!” she shouted through my lips.

Ugh. Anyway, he knows that’s her and kisses actual her this time, but she bites him anyway because Melanie’s primary characterization at this point is rabid jealousy, and

He started laughing. “That’s my girl.

because women can’t actually hurt men, and it’s so cute when they try to!

Melanie says she doesn’t remember anything or know where she was in the brainslug’s head.

Jared asks if the brainslug can let Melanie out, and she tries but can’t figure out how, because she is incompetent and doesn’t know how to do anything, and is too stupid to consider just letting go of some of Melanie’s brain.

So Jared kisses her again.

She jerked our head back. “Cut that out! Don’t touch her!”

And it’s interesting, I think, that Melanie’s allowed to vocalize distaste for theoretical cheating by her boyfriend but mostly kept silent when it comes to herself being groped by someone she doesn’t like.

I won’t erase you, Melanie. I’m sorry I can’t give you more than that.

You could get the fuck out of her body, brainslug.

Thank you.

You know what would be interesting? If this wasn’t Melanie at all but the brainslug suffering from a delusion brought about from the confused memories and too-strong feelings. That’s why she never seems to have any feelings of her own but is defined around the other people in the brainslug’s life.

I mean, let’s consider her objection to being touched by Jared. The brainslug knows Jared loves Melanie, not a brainslug in her body, and he’s also very violent and dangerous to her. But she’s uncontrollably in love with him and can’t resent or fear him properly, so she outsources the objections to “Melanie”. Jamie, in contrast, doesn’t seem to care as long as he’s got something that looks like his sister caring for him, so she hasn’t needed Melanie for that, and it’s only when he expresses interest right now in hearing from his real sister that she panics. And the whole Ian section basically reads like an adult trying to talk an eight year old into sex with his whole does it feel good does it feel okay if it doesn’t feel bad we should keep going stuff. She doesn’t know how to object within that framework and isn’t sure what she wants to do anyway, so “Melanie” categorically rejects him for her. It works all the way back – she was missing Melanie’s family because of their memories and it was easier to say Melanie was making her do it, talking her along, so she didn’t have to think about what it really meant. (And that’s why “Melanie” can figure out the lines all of a sudden when she never did in all the time before – the brainslug worked it out from her memories.)

“What’s she saying?”
“We’re just… making up.”

But the brainslug doesn’t want to be hated, so “Melanie” is fine with the basic setup of losing her body and never asks to be freed.

Jared wants to know why Melanie disappeared and why she can’t take control of the body.

“I don’t know, Jared. There really isn’t enough room for both of us. I can’t seem to get myself out of the way completely. It’s like… not like holding your breath. Like trying to pause your heartbeats. I can’t make myself not exist. I don’t know how.”

Yes, you do. You disconnect your filaments.

I wonder if this is some body/soul dualism thing where the author just can’t accept that the personality is only in the brain even when she’s set up that as a fundamental part of her plot. The brainslugs grip the brain to control it and suppress the host personality, so doing the opposite should work fine, but she metaphorically tries to get out of the way rather than literally.

He didn’t answer, and my chest throbbed with pain. How joyful he would be if I could figure out how to erase myself!
Melanie wanted to… not to contradict me, but to make me feel better; she struggled to find words to soften my agony. She couldn’t come up with the right ones.
But Ian would be devastated. And Jamie. Jeb would miss you. You have so many friends here.

See? It’s all absolutely what the brainslug would want to hear, not what Melanie would feel. The fact the guy she loves wants her freed is totally irrelevant in the face of comforting the brainslug about how much people like her and how she should keep imprisoning Melanie.

Bringing Melanie back had not saved him. All that I could do was not enough.

So yeah, that’s confirming that saving Melanie herself was never a concern.

Jamie’s immune system is apparently shit and he’s dying of fever. The men went out to look for antibiotics:

“Did you check –”
“Every spot we could think of,” Kyle interrupted. “It’s not like painkillers, drugs–lots of people had reason to keep those hidden. The antibiotics were always kept in the open.

Actually, my family’s got a pretty good cache. Mostly ones for animals, but you don’t seem too picky at the moment.

If they dug a hole for Jamie in the empty desert, they would have to put me in it, too.

Incidentally, Melanie is not in favor of plan suicide, which is irrelevant to the brainslug. Luckily she’s also in favor of plan doing shit, and the brainslug grudgingly decides that’s the better one since it involves Jamie not dying. They just need to go get brainslug medicine! Yes, you fucking pack of morons.

Jeb looked at me. “Hon, we can’t just walk in there and ask.”
Right then, another very simple and obvious truth occurred to me.
“You can’t. But I can.”

Christ, that only just occurred to you? Seriously, everyone in this book is so stupid.

Think of it! I could get enough to heal everyone here. To last for years. And Jamie would be fine! Why didn’t I think of this before? Maybe it wouldn’t have been too late even for Walter.”

She is, of course, shocked that they don’t trust this, but frankly I wouldn’t either, because why didn’t she think of it before? Why wasn’t the fact your people could fix Walter the first thing to occur to you. Sure seems like she was deliberately waiting until she thought they trusted her more before suggesting this.

Anyway she’s told now and goes into a dramatic episode.

My knees buckled. I fell forward and yanked free of Ian’s hands when he tried to pull me back up. I crawled to Jamie and pushed Trudy aside with my elbow. The silent room watched. I took the compress from his head and refilled the melted ice. I didn’t meet the stares I could feel on my skin. I couldn’t see anyway. The tears swam in front of my eyes.
“Jamie, Jamie, Jamie,” I crooned. “Jamie, Jamie, Jamie.”

This is just really not convincing, brainslug. It’s so hideously over the top.

He would slip away from me. Tomorrow. The next day. And then I would die, too. I would not live without Jamie.

Put like that it sure is selfish. That’s what all love in this seems to boil down to – concern for others because their physical presence makes you feel better.

Jared then comes back later and knocks out the incompetent doctor guy with chloroform. The characterization of this may be an endless clusterfuck, but I do appreciate that the physical setting actually seems quite accurate. In every other book I’ve seen that’d have been done by punching the other guy in the head or something.

He blindfolds her for a bit, which seems pointless because he says she’ll be killed if they’re caught, so it’s not like her being blindfolded and not knowing the way would be a factor in their decisionmaking.

Once they’re out, he gives her a poison pill in case she’s caught and they’re going to read Melanie’s memories.

“It’s not a joke, Wanda,” he said angrily. “If you can’t do it, then I have to take you back.”
“No, no, I can.” I tried to get a hold of myself. “I know I can. That’s why I’m laughing.”

I thought this was because it’s unnecessary since brainslugs have that brainshredding attack. But no:

“Don’t you see? For millions of my own kind, I’ve never been able to do that. Not for my own… children. I was always too afraid to die that final time. But I can do it for one alien child.” I laughed again. “It doesn’t make any sense. Don’t worry, though. I can die to protect Jamie.”

This really only makes sense if you view potential children as equivalent to currently living ones.

Then he gives her clothes to change into and she gets embarrassed and turns around while she’s changing.

Another engine came to life, quieter than the jeep’s. I turned to see a modest, unremarkable sedan pull out of a deep shadow under a boulder. Jared got out and chained the tattered tarps from the jeep to this car’s rear bumper. Then he drove it to where I stood, and as I saw the heavy tarps wipe the tire tracks from the dirt, I comprehended their purpose.

That’s quite clever, book.

“Jared. I can’t go in with my face like this.” I pointed to the long, jagged scar across my skin.
“What?” he demanded.
“No soul would have a scar like this. They would have had it treated. They’ll wonder where I’ve
been. They’ll ask questions.”
…
“What do you propose we do, then, Wanda?”
“I’ll need a rock.” I sighed. “You’re going to have to hit me.”

Naturally.