I think your SD is very clear-thinking. I think she pretty much stated what we all want from the As in our lives:
'the only thing I want from my mum is for her not to be an alcoholic'.
I think I started leaving my AXH when I realized that it was no longer enough for me if he quit drinking. Or got into a good recovery program. I really wanted for him not to be an alcoholic. I wanted him to be an equal partner. I wanted him to let me listen to the music I loved that he hated. I wanted to be able to have friends that he didn't like. And as I went down the list, I think what it boiled down to was that a) I wanted him to not be an alcoholic and b) I wanted him to be another person than he was.