How do I deal with this?

Just walk away, because if you don't, she’s going to destroy you.

And if you're lucky, maybe she'll actually let you go.

The truth is, she needs you just to feel alive, not because she loves you or even cares about you. Even if she did, she wouldn't know how to act any other way.

You fall in love, and eventually, it just fades away... maybe you’re just addicted to the chase, drawn to someone who feels completely out of reach, someone you can't quite win over. That's usually how it goes. I’m sure she’s attractive and has a great personality too, but if there really is a mental health issue involved, then she needs professional help. It isn't something to be trifled with...