Love the thread title.
Went into work today and ended up leaving at 1915, but feeling much better now (apart from the long day).
Called my mother re Christmas and asked her when she wanted DH to pick her up. She told me (long pause for dramatic effect) that she wouldn't be coming to us because:
She didn't feel welcome
It wasn't Christmassy enough
All she did was sit in a chair
All we did was eat, drink and watch telly.
We didn't go anywhere
We didn't play any board games
I just said, that's fine, have a lovely time in Eastbourne with Edna.
In my defence of the above:
DH schlepped out to collect her and took her home again after Christmas rather than her coming on the train.
We had a 7 foot tree that was dripping with decorations, fairy lights a go go and Christmas music playing non-stop. What did she want, Santa's Fucking Grotto?
We offered to take her to see her brother, her sister-in-law or her friend, or anywhere she wanted to go. She didn't want to go anywhere. She wouldn't leave that fucking chair.
What is wrong with eating, drinking and watching telly at Christmas? And the food didn't cook itself - she could have peeled a potato.
We did play Monopoly. And Uno. She refused to play because "DD2 cheats and you always win Monopoly and it's not fair." 
I'd put good money on her and Edna falling out big time, the hotel being like God's waiting room and her hating it. I hate to say it, but the relief of her not coming for Christmas is huge.
Rang Cousin Z to rant, and she said not to worry, I'd never be able to please her and not to bother trying, and that everyone knew how difficult she was.