Just quit! It's not as if you're breaking it off with a boyfriend. I doubt she's gonna kill you though she might still be stubborn.. Just tell her like this
"look b#tch, I'm sick of your sh$t! You put my sister though hell last year and I refuse to go through the same. Now you take this club and shove so far up your a@# your ribcage will be hanging on for dear life! I QUIT!!"
Than in the midst of her venting toss a chair at her and walk out.. And that's all there is to it.. Give it a go and good luck

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