... she sure knows a lot about human psychology. I say that because of how she talks to the disfigured man. She knows how he's feeling without him saying or even doing much. What's odd is that every other scene shows her as someone who's learning basic human behavior. I would consider calling it a plot hole, but it's hard to do that with an ambiguous story.
My thought on that was that it's precisely because she's newly learning humans, that she's able to relate to him. No preconceptions.
Also, she and he are both different from those around them. So that's a point of commonality. She may feel some kinship in that.
But mainly I think it's because she is discovering him without judgment, fear, or disgust, and he can see that, having had a lifetime of all those reactions. There's no visceral rejection of any kind. Only curiosity, acceptance, and invitation. He, naturally, responds positively to that, if with caution, and opens up to her.
Wow. You wasted those spoiler alert tags in your post. Your title is pretty much one big spoiler right there. You might want to think about wording your titles AND your posts a little more carefully. There are people who come here to get a feel for how well a movie is liked by others before they watch it, and titles like yours kinda screw the whole experience up for them.
I know this was posted a long time ago, but you should know Netflix's one-sentence description tells us all the same information. Not saying that's a good thing, but it's definitely not a secret to anyone watching this on Netflix that she's a man-eating alien.