I was glad to read towards the end there that you do not want to entirely give up on the relationship. But throughout reading all these posts one thing became clear, your friend is struggling. You stated it's not just with you but also other people notice it. You also stated you have tried to talk to her about these things with no luck. I wonder though if you shouldn't give it one more try, perhaps from a different perspective. I can tell from your posts that your feelings are hurt by what she has done, and I think that's an appropriate reaction to how she has treated you. BUT, I don't think this is about you.

I mean no offense, but one thing in there you stated hit me a bit wrong. You said

"And I think if we were ever to be friends again, I would need her to, on her own, apologize for how she has been treating me without me having to explain all the ways she has hurt me."

I think if she is really hurting (which I have no doubt she is from what you say) that maybe it would be good for you to meet her halfway with this. I like the idea stated earlier of a letter if in person contact has been unsuccessful. Perhaps you could share with her why you are hurt, even though I'm sure it feels as though you shouldn't have to. I really do understand THAT feeling. However, in her state of hurt she likely cannot see how she is affecting others around her. And I also think to express real concern for her, and to share with her how important your friendship is with her. I don't mean to presume you haven't done some of these things, but it sounds like not all options have been explored and I think your friend really needs help right now. She may still reject it and not be ready, but at least then you will be able to feel as though you have done everything you could to help her and your relationship with her.

Sorry for the long reply, but your post really grabbed me. Good luck, and I hope to hear more about how things turn out.