Thanks! The attraction might have a bit of a physical level, since both of them do pay attention to each other's faces, but most of it's mental, as you assumed. Their opinions are important to each other now, and that's already a big change from Hogwarts, where they had to pretend with all their might not to care what the other boy felt. I think they're both still expecting it to blow up, hence the way they're dancing around each other.

Hermione doesn't know the whole story yet, so right now she's feeling that Harry is trying to abandon both her and Ron. But she'll learn better in the next chapter.

They'll still have to learn how to manage the compatible magic, at least a bit, to keep it from draining them. But that's in the future.