I'm not a mother, but here's just my humble input - (not that I think you have not tried this already!) What would happen if you told her:
"Mary", I love you, and I will never abandon you.
I want what is best for you.
I want you to be happy.
I will help you in any way you need.
I don't like you saying nasty things to me, but I still love you.
I will not accommodate or accept your bad behaviour.
If you are scared, tell me, and I can help you.
Nothing you do, will make me love you less.
Sometimes I don't like what you do and say, but I do always love you, and that's why this bad situation makes me unhappy.

I could imagine that I would have wanted to hear these things. For what it's worth