I think completely ignoring her is the best way to go.
She is a vitriolic and poisonous piece of flotsam, but why give her the time of day?
I know someone who has fallen out with his mother because she is angry for him moving out and her losing his £400 a month board money, and her having to move to a smaller property now (even though his 1 year younger brother moved out 5 months before and she bid him farewell with a smile.)
The woman was toxic, and vile to the lad anyway, shouted at him for fuck-all, made him do 50% of the household chores, called him stupid, and said he was a thick cunt like his dad. (she split with him 10 years ago when he left her.)
So when he (and his girlfriend) moved in together, his mother said 'don't ever come back, you're dead to me. And SHE can fuck off and never come back too!' (Meaning the girlfriend.)
He said 'bye then,' and left. He was upset at first, but after a few months, he became more confident and happy and could LIVE and enjoy life without mother screaming in his face. It's not like it wasn't TIME he moved out; he was 23 and had been with his girlfriend for 4 years! The mother wrote poisonous vitriolic bile on fakebook about him AND his girlfriend, and they said
Not.
One.
Thing.
Back.
They just blocked her from fakebook, and she was incensed.
And this was a year ago that he left, and it has eaten this woman alive that he never looked back, never responded to any taunts or goading, or nasty comments aimed at the girlfriend, and never said anything back, not even to anyone else.
She did send several messages after about 5 months, like 'you have some post here,' (to his phone,) but he deleted the messages. And after a while got a new phone. In addition, the girlfriend ignored her, and so did the girlfriend's whole family. It was hard for the girlfriend's family as it was their daughter she was badmouthing, but it REALLY fucked off this lad's mother that NOBODY responded to her bile.
I went off on a tangent there, but suffice to say that the best way to deal with vile angry toxic people, is to IGNORE them. Drives them fucking nuts, because they are not getting the attention and responses they crave.
if I had been the OP, I would have not even acknowledged KH. The woman makes my skin crawl.