See I think you're just over thinking it. The fact of the matter is that she does not treat you the way a friend should. There's no question that you've been a good friend to her, so you shouldn't feel bad about that. She obviously has issues so she's just going to distort whatever you say/do and make you out to be the bad person - either to make you feel guilty, or to make your mutual friends think you're the reason you two don't talk anymore.

It's hard when you know you have to be the bigger person, but that is what you have to do here. You just have to accept that she isn't the same person you used to know and love and move on with your life.