I pretty upset for quite a while when I first heard.
I've been frustrating her mother for a little while now because she wants to lay into me about how I've treated her daughter, but I've stopped standing there taking it and answering back just encourages her. I've hung up on her at least once, and I've walked out of rooms several times. A few times I've informed her that her memory of events is faulty and left it at that. She has resisting accepting that I will not discuss past events with her whilst she is being combatative and certainly about things I can't change.
So I'm already having as little to do with as possible. And made it clear that it's her mother who is inflaming things.
Wade.