Is she just clueless and self absorbed? Does she get gifts from them or something? I do stay in contact with my stepmother, they were married 25 years. I don't quite avoid my father, as many in my position would probably write him completely off, I keep my distance.
I see women all the time, maintaining contact with their moms despite their pasts, not always perfect pasts, but mom is mom and you only get one.
I've heard of distance between father and son when divorce occurred at a young age, in many parts, I point my finger at the mom. Yet, in your case...vent away! You've hinted at disrespectful comments in one of your first posts. What's your daughters deal??