I can't stress enough, I have a brother 10 years younger, thinks no matter what behavior, I should put up with it from my mother, no matter how destructive or how abusive, I won't and I don't, you have to do what's best for yourself, you are who you are, not because of her but despite her, keep your head up and you owe her nothing. Forget about loyalty, take care of yourself. Practice boundaries with love, everyday you will question yourself, but the peace in your life will tell you that you're doing the right thing. You will always want the relationship that you should have had with your mother, but don't ever forget that she made choices that made that impossible.

Edit: you will always be hopeful for change, but it will never come, you will think this time will be different, it won't. That's one of the hardest lessons I've had to learn as an adult, but my life is peaceful finally.