Christ I could have wrote your post OP. Firstly. Block the horrible nasty piece of work that is your mother. I finally decided to not tolerate my 'd' Ms shit in my early 30s and I can tell you it was the best decision I've ever made.
My mother also claimed she had a terrible childhood, and thats why she was abuosve to me. Either that, or it was my fault for being a terrible daughter and human being.
The reality is, my mother disliked me from the moment she could no longer control me. She expected a perfect child who was a mind reader and when I failed, was punished, hit round the head with a stick, thrown out onto the streets at 14, whilst the golden child, only left home aged 40ffs. She also favoured neices and nephews and enjoyed showing me how much she wish they were her children, not me.
She loved my abusive exH. I always suspected it was because she believed he would keep me down, in my place and she enjoyed that.
Well, no fucking more! I decided after the straw broke the camels back, to go NC and I haven't looked back. For over 10 years I've not heard a peep, until I had my DC and, guess what!? She wants to be in touch. So reluctantly I meet with my DF (also treated like yours) and DH tells him a full apology was in order. Later that day, a text starting, were sorry, followed by abuse that it was my fault they behaved like that.
Here's the thing you need remember, and what I told them after that, 'I will not allow you to blame me for how you behaved when I was a child, do not contact me again or it will be considered harrasment and reported to the relevant authorities'
Life is good again. The witch is back in her own home where she can't reached me or my DC.