This is just my opinion, and I am only getting the little bit of the story that one can get reading it on a forum posting.

I like your idea about not contacting her again. I would not even contact her on her birthday. You guys broke up in March, but by staying in touch all of this time, you haven't had to deal with all the pain of breaking up. It's like it is coming to you in dribs and drabs, as you hold out hope that one day she will feel better and you will reconcile.

I would not beat yourself up about the things you may or may not have done wrong. It takes two to tango. She sounds like she has some serious problems, and while it's nice that you want to help her, you can't fix those problems.

So my advice would be to detach from her and start moving on to new friendships and new relationships. Maybe some day in the far future (i.e. years) you two will reconnect as friends -- but for now, she has said twice that she wants to be left alone. I would leave her alone. If she reaches out, I would probably still leave her alone, because who needs that kind of emotional drama in their lives?

I hope it gets easier as time goes by. Good luck with whatever you decide to do.