Loreli, my grandmother was horrible.
I now know, 20 years snce she died that without doubt she had narcissistic personality disorder, absolute classic case. Favourite child, very controlling, scapegoat child, no one in the family could dare to contradict her, was always having a "drama" or ill, she was always right etc etc.
Anyway she made it her life's work to make her son in law and daughter in law's life a misery.
The daughter in law was my mum. Granny was horrible to her, told her she was an unfit mother, my brother's asthma was mum's fault, his eczema was her fault, my greasy hair was my mother's fualt for feeding me badly. She told everyone my mother insisted on a new car every year, this is rubbish, it was my dad who did that as he drove so many miles. She controlled everyone and everything and no one in the family dared say anything to her, in fact, they were so used it it no one stood up to her in about 30 years. My mother did try to defend herself, but got no help from my dad.
It caused huge issues with my parent's marriage, and when gran had been dead years and my mum was dying she turned to my dad and said "why did you never defend me against your mother?" When my dad was 80 and mum dead 10 years I FINALLY got him to admit his mother was a prize bitch, but I really wish he had stood up for my mum and not let her take all this shit.
Luckily my MIL is fine, drives you mad with illogicalities and inability to make up her mind, but she is not nasty, or vicious, or spiteful and she doesn't tell lies about me, so she is great, but my gran was horrible.
Due to my experience I can now spot families where one person acts VERY BADLY almost all the time and all the rest of the family walk round saying "oh, that's just how they are", "you are over sensitive, they are fine" and I just KNOW that there is a very controlling person who has bludgeoned her entire family into accepting what is socially unacceptable behaviour. I always avoid people like that now.
All you can do is tell your DH that her behaviour is bad, his denial of it makes him complicit, and how hurt you are when you put her feelings above yours.
My mum finally stopped seeign gran and stopped us kids going, for which we were extremely grateful.