Momma_Cluck has said it all,
just walk away, have no contact with her.
Don't try to explain anything, she refuses to understand or listen.
The probem is hers. Not yours.
Walk away and cut her out of your life, believe me, if you don't feel good walking then run.....
I am one of the mugs who gave in to these kinds of behaviour because I didn't have the self confidence to hurt anyone else. It ruins your life.
RUN.
I am being really serious, I am now 55 and have serious issues trusting now. I also look back and wonder about all of the good things I could have been doing while I was supporting problem people.
Lift your head, look life in the eye and find people worthy of your trust and effort.