The sooner you leave home, the better and then you can be in control of how much time, if any, you spend with her.
You will be able to up and go as soon as things start getting uncomfortable, which will then give her time to assess her treatment of you.
I really can't see any other answer to the situation, as you have tried to talk to her and you seem to be getting nowhere due to her refusal to admit she is being a cow to you.
My mother was much the same; only with me though (I have 5 siblings)... you can read about her treatment of me here.... post451715.html#p451715
I came a long way in resolving my issues with my mother before she died, but even now, I can't accept that she treat ME differently to the others. I am the third born and you know what they say about middle children. I think she desperately wanted a boy when she had me (she already had 2 girls) and she resented me for being a girl. she eventually had her 'precious boy' after having 5 girls!!
My mother was selfish and greedy.... other people thought she was wonderful and she praised us all highly when with others. But, to our faces, she could be extremely nasty. She was extremely beautiful when she was younger and she was the youngest of eleven children, so was spoilt rotten by her siblings. She was very jealous of what others had and I suspect only married my father because his parents had a very successful building business. She was gutted when, after they married, my father decided not to join the family business and spent her life resenting the luxurious lifestyle of her in-laws. She was very bitter, very vain and very greedy. She made my father suffer for his decision, even though he worked very hard at his chosen profession to provide for her and 6 children. For the last 15 years of her life, she never spoke to my father and made his life an utter misery. She was a huge drinker and smoked a lot, and hated the fact that her looks didn't last very long, which was sad really, as she was certainly a looker!
But anyway, I could go on and on about my 'dear' mother, but to get back to you, Lilycat.... I don't think your mother will change, unless she is prepared to accept responsibility for her treatment of you. I doubt she is going to do that, so the only way of going some way to resolve your issues, is to move out and for YOU to be in control of the time you spend with her.
Good luck. x x x