Her mental health is NOT your responsibility, and this is beyond your control. Telling her father is a good step, and you need to let him know that the two of you can’t be together - she needs to focus on getting help. If he or other family won’t deal with it, then get authorities involved. But you have to tell her that this is not normal and safe and she needs to get serious help. The two of you cannot be together - it’s toxic, and not healthy for either of you. You will feel trapped, fearful, guilty, and overwhelmed with responsibility. She will end up dependent on you for emotional stability, and not nipping this in the bud now will only convince her that this is “acceptable behaviour”, and she will continue to act this way, and likely resort to more extreme measures. She can’t be in a relationship until she is able to take care of herself. She will act out, be angry and blame you, but this is NOT your fault. Taking responsibility is an acceptance that one has a problem and needs help, so it’s easier for her to try and make it your problem.

I understand mental illness and have been through SH, and this is not something that just goes away. She needs medical assistance. But you have to be strong and walk away and let her family look after her. This is not on you. Good luck.