I would suggest looking up the possibility of Borderline Personality Disorder.
http://en.wikipedia.org/wiki/Borderl...ality_disorder

I wouldn't say that the unstable relationship pattern is typical for bipolar, because anyone with bipolar could have varying degrees of awareness of their condition. Some people with MI learn how to treat relationships in a much less destructive manner. The only advice I could ever give you regarding relationships with the 'mentally different' is: to be supportive, press that she seeks professional help, and to encourage healthy coping behaviors.

It seems to me that you put your share of effort into helping her feel better, but she doesn't yet have the control over how she acts in response to how she feels. She feels really vulnerable, and perhaps her insecurity is driving her to volatile attachments. And in the case of BPD, the acting out would be an attempt to garner emotional support (?).

It is awesome that people like you exist who are willing to look past emotional abuse and see the scared victim of mental illness on the inside! But on the flip side, the victim is still responsible for the continued heartbreak they put on others.