Is it possible for you to write her a letter including everything that you feel towards her? Since you don't believe confronting her is possible, you wouldn't even need to be near her when she reads it. I'm in a similar situation here with my mom (its been this way forever) until I move in the coming weeks. I wouldn't want you to assault her because of your future. Plus, if you had to go to prison, we'd miss you on here too much.
I'm sorry for your situation. It angries me how people like that can still...exist. I wish i could give you advice, but I'm pretty bad at confronting people myself. Maybe just ask her like...why is she being such so hard to live with...and to just chill off..that both your lives would be better if you just got along.
Good luck with the bitch