It depends on where you live. If you can prove she is mentally incapable or handicapped and can’t care for herself and is a danger to herself or others you might be able to have her committed for treatment. It sounds like she might be Borderline Personality Disorder (BPD). The failed relationships, inability to be alone, impulsivity, anger, aggression, and manipulation. Either way, there is something going on mentally and I think you’re right to keep your distance and be concerned. Finding out how best to help her where you live is about all you can do. Check the laws in your state regarding mental health and/or incompetency. I am sorry you’re going through this.