Mental Health Support

First, I am really sorry you're going through this. It sounds really depressing for any parent to have these types of social dynamics going on. I had younger twin sisters so it was a very different situation, which them competing with each other at first, then going off in completely different directions so they could not be compared to each other at all.

Does this syndrome coincide with any personality disorders?

I've definitely seen mothers turn their children against a father, especially one who is accused of some cultural wrongdoing, or in the case of divorce.

It's kind of a strange behavior from the survival point of view. Maybe the daughter is competing with the mother, but it seems like the benefit would be really small, maybe only mattering to shore up the ego? (That's why I wonder about a concomitant personality disorder).

Wow, I sure hope this calms down. Nearly all of the annoying, bad things we three kids did when we were younger resolved as we matured. From time to time, old patterns reemerge, though.