In all seriousness, how do you know this? It IS possible that your daughter made her own mind up. He isn't isolating her. She goes to school, to work, I assume she has friends, she sees her father and talks to her sisters. Is it maybe just the way you want to see it? A cult leader? Really?
Not trying to be harsh, but maybe a jolt of reality?
I would love to blame my son's wife on his lack of interest in the family, but I can't. He is an equal participant in it. She may have given him ideas, but he is the one buying what she is selling. You seem to absolve your daughter of all blame here. I doubt that he alone is feeding her nonstop hate. Something else is going on that is in HER head.
