I would be so grateful if you can help me formulate a good response to this situation. This is long, sorry. 
My DM had an appalling childhood. Her parents were abusive (including sexually). She was the youngest out of 4. She was scapegoated alot. She is now in her late 60s, but still runs around trying to appease her family (siblings only now). I think of her as behaving like a puppy desperately trying to get attention and approval. My DDad refused to have any more to do with them from when I was a child and I used to go with her on her visits in order to support her. I can honestly say that it made me miserable. She would take everything out on me. They lived three hours away and she would usually scream her head off at me for some imagined transgression that 'showed her up'. She would repeat what her parents said to her. I was disgusting, a horrible child and person, what did she ever do to deserve a horrible child like me etc. As an example, when I was about 12 my uncle kissed me hello at Christmas by shoving his tongue down my throat and grabbing my boobs. I yelled at him and my mother smacked me hard across the face and hissed; 'I don't care what anyone does to you, you never be rude'. I have a hard time forgiving this to be honest. There is more, but I don't feel up to talking about some of the details, even anonymously.
Anyway, I have refused to see the family for about 5-6 years now. (I am 43). My mother often laments and says; 'But they always ask after you, they really care about you'. (They don't). BUT, my mother goes and stays with her siblings 4-5 times a year. She is there now. What happens is that she then will come home crying and will wail down the phone to me or on e-mail about how horrible they are and what who said to who etc.
I usually respond calmly by asking her to consider why she is in contact with them. Apparently it is because they are her sisters, she loves them blah blah. I have had her sobbing on my shoulder just this past 6 months or so. I am tired of it.
So, DDad calls today and says that she is staying with The Horribles so to expect the full drama in a day or two. This is what I want to say to her;
'Mother. You go in circles with your relationship with them, and they only cause you pain. I have tried to support you for years. You still seek out being in situations with them that hurt you. I am afraid I do not want to hear about it anymore.'.
Too harsh? I do not want to hurt my mother, who is 'very sensitive'. But I also want to say 'Grow the fuck up woman and stop dragging me into your crap'.
An essay. Sorry. Any thoughts, advice, very very very much gratefully received. 