IMO, I would absolutely refuse to lower myself to her depths.
By being the adult here, (that would be you) you are in fact teaching her how you want to be treated.
By responding to her vicious, small minded, attacks on you, you would then be putting yourself back in her grips.
Put her on ignore, and live your life the way you see fit.
Let her and her H.P. who she is supposedly so close to..(bit of sarcasm there) work it out. It really has nothing to do with you. You did nothing wrong as far as I see it.
Hugs, and peace.