C.C.
Since you can't move away and create space maybe you can create space in a different way. Stop letting her come around and spend time with your child. I know it sounds mean but do you want her treating your child the same way she treats you someday? Sometimes it takes being deprived of something to see what you are doing is wrong. Maybe after a month of no contact mom may call and find out just what is going on and then you can tell her how you feel with the ball in your court. You are a grown woman who is raising a child and working full time and she should show you the respect you deserve.
My mother is gone now but she was tough. I can remember yelling back at her some of the things you are talking about. Like "I not your child anymore! I am Doug's mother now and you will treat me with some respect." Or "stop being such a martyr! "
Good luck and remember you are the boss, you just haven't realized it yet.
And one more thing, Try to have a frank conversation about her health. I just remembered that the worst of her bad behavior happened when she found out she had cancer and wasn't telling anyone.
Good luck