You know, someone recently recommended the book, "Divorce Poison", and aside from getting the woman's diagnosis from a psychologist, which helped us understand that lots of her behavior was not something she was willing to change (or that she didn't understand that it was wrong), this book is amazing in it's help in figuring out how to counteract some of the nastiness they encounter at her house.
My husband & I are really finding some interesting new ways to resolve some of this stuff by reading this book, and I have high hopes that the results will be that everyone will be much happier. We hope. The book's recommendations make a whole lot of sense, so we'll see.