@divine1966 - this is why I think she has a recognizable behavior pattern. I doubt she'ld ever be willing to consider that. I'm sad to think that this may never change.

I also have another sibling, with similar issues, only way, way worse. My brother gets arrested on a regular basis for his intemperate behavior. I've read that males who are chronically in difficulty with the law tend to get diagnosed as having antisocial personality disorder. Some researchers believe that, often, these men would more correctly fit the category of BPD. My brother seems like he could qualify for either category. But I've always noticed that he seems mainly driven by extreme insecurity. He has very unstable identity. He's very clingy to anyone he thinks is a friend. Then, if they disappoint him in any way, he feels unforgivably betrayed. Ten years ago, he wanted me to share a house with him. (Not that I was interested.) Subsequently, I denied him an unreasonable favor he wanted. He hasn't spoken to be since, in about 9 years.

Maybe it's just as well that I do live far from family.