I too had an horrendous mother, well, still have. She has done many things but, due to getting to know my dad better these last few years, a lot of the things she did were kept secret, including an affair she had for many years while still married and while we were babies. At one time, I questioned myself if I was actually my dad's daughter and I shouldn't have had to do that. She had a relationship when divorced with a man who was into things he shouldn't have been but she would not hear a bad word said against him and wanted us to invite him to our houses. Belting us for wanting lunch, locking my brother out of the caravan for an asthma attack, didn't do anything when my sister was attacked, took knives to my dad in arguments, drunk to oblivion. And some of this is being played down for on here.
I sent her a card a few years ago saying thank you for the stuff she had done which was lovely, good meals, parent's evening, sports day, cuddles. And I said that I forgave her the things which weren't lovely. She has been in touch because of my dad dying but now I don't want anything to do with her at all. I have no feelings now either way for her. I am too busy concentrating on what is wrong with me and enjoying every day. I won't forget, but I am not going to let it rule my life any more, time is far too precious to waste on someone who did not put me first when she should have done. And she would still be the same now if I was to try to have a relationship with her.
I do think that a line can be drawn under bad relationships if both parties are willing to try to make a go of things being better and different. It's no use apologising if things are not going to change.
It is awful to read this thread but it does show that we have not been on our own in our abuse from our mothers and that, for me, gives me some comfort, even though I don't like the thought of others suffering too.