Quote 55
I pulled away again. "What about Lara? Jake?" Again, she sshed me. "Less tongue, more lips," she said, and I tried my best. (thelastday.73)
Oh Miles—he tries to grow a backbone about making the right choice, but he still lets Alaska choose for him. Granted, he doesn't try very hard to stop kissing her.
Quote 56
We did not say: Don't drive. You're drunk.
We did not say: We aren't letting you in that car when you are upset.
We did not say: We insist on going with you.
We did not say: This can wait until tomorrow. Anything—everything—can wait. (thelastday.93-96)
Everything that Miles has chosen—or not chosen because of his passivity—leads up to this moment. He could have been much more active in preventing Alaska from going, and the Colonel—arguably—should have been more assertive about Alaska's choices based on past interactions with her. But they both chose passive acceptance of her decision. Why?
Quote 57
So we gave up. I'd finally had enough of chasing after a ghost who did not want to be discovered. We'd failed, maybe, but some mysteries aren't meant to be solved. (118after.1)
Miles and the Colonel find out as much as they can, but then they quit because they "failed." This doesn't sound like a choice at first, but it is a choice they make. Consider why they choose to leave Alaska's mystery unsolved.