I'm sorry to hear about how you've been treated, and I wish you all the best. Your ex-gf's behavior might be the result of any number of psychiatric disorders (from BP, borderline personality disorder, depression, ADHD, etc.) or life circumstances (trauma, abuse, etc.). Only a professional doctor who is seeing her in person can diagnose her, and even then, misdiagnoses are possible.

She is an adult, and the fact that she is suffering cannot be used as an "excuse" for the fact that she needs to be responsible and get help. You may care about her, but she is responsible for herself, and you are not her caretaker. Does she regularly see a psychologist AND psychiatrist? It sounds like she needs a dedicated, responsible professional team to help her (i) sort out her life and (ii) become more responsible for herself.

With behavior like this, it might be a good idea for her to start off by seeing a psychologist. He can decide whether your ex has an underlying mental disorder (or some other source of problem), and where to go from there. Regular therapy is critical. The fact that she had a psychotic break is indicative of some kind of long-term problem.

I'm not saying that you should get involved with her treatment -- she has parents and herself, and she should be able to rely on those sources. You should not feel responsible for her in any way, or guilt-tripped into sticking around for her. Your ex clearly understands that she has a problem, and it's her own responsibility to get help at this point.

I wish you the best, and I hope that you find some peace and comfort.