PS to add - My family thought I was hell on wheels for a few years while I was married to a narcissist control freak. I was not a nice person to them. He had me convinced my family was dysfunctional and that he was going to "fix" me. I was young, had very little sense of myself, and easily manipulated. Perhaps that's a little bit like what is going on with your sister. Don't know. It's a thought.