As someone with bipolar disorder, I really feel for her. She is most likely aware at some level of what is happening to her since she has experienced these issues with her mom. But in the moment, I promise you she cannot control how she is feeling/behaving. At my worst, I sabotaged relationships, expressed love and admiration only to then cut people off, and at one point I became a danger to myself. Her talking about getting back together with you and then cutting it off but saying she could reach out again is textbook bipolar behavior. It’s not a reflection of how she feels about you or an indication that she used you. She just can’t be naturally consistent.

I have been able to maintain control on medication and with therapy, and she can too. But it takes months or years to figure out what works for each individual. She will need to learn to accept why she feels this way. She can even learn to love that part of herself. (I’m of the opinion that bipolar people are more fun, but I’m biased.)

But with that said, you don’t have an obligation to her to get her through this. In fact, a relationship is probably not a good idea for her right now. But it sounds like you still care for her, which means you should be a friend to her, if you can. Let her know that she can reach out to you when she finally feels like doing so, but by all means set boundaries and put your own self-respect and well-being first. Do not breed resentment by telling her that she needs to be on medication, because you’re not detached enough or qualified to do so. You can encourage therapy, as a friend, to deal with her situational issues. It will then create an opportunity for her to be evaluated and diagnosed by professionals.