Happy Birthday, m'dear! And, what a year it's been, eh?
Your mother can't hide her behaviors anymore because she can no longer control her own impulses. There comes a point where the ususal management tactics are no longer effective - it's true with all mental diseases and personality disorders. Her hatred is a phantom in the Real World, Lakelight. It's misdirected at you and your husband because that hatred (such a passionate emotion) is threatening to melt her down if she were to allow it to turn on her Self. She is a sick and pitiable human being.
Angry? Heck, YEAH, you're angry! And, it's righteous. I've said this in posts before and I still feel that experiencing the anger will give way to sorrow and, finally, acceptance. I recommend the book, "On Death and Dying," by Whatshername Kubler-Ross. Whenever something "dies," we have to face the process of grief. And this book addresses it all, whether we've lost someone physically or emotionally. A loss is a loss, plain and simple. Physical death makes more sense because it's cut-and-dry: the person's body failed and they passed. Emotional death is something that is indescribable, for me. It's like being skinned alive and having salt sprinkled over the exposed tissue.
You've done well for your Self and you are not responsible for your mother's actions OR her menal illness or personality disorder. Hopefully, her physician will notice the downward spiral and take appropriate steps.