I think she is being snarky because she is trying to get a rise out of you, and it's not working. You are not behaving in the same old way you would have in the past and she is confused by it. As 2 said, it won't fit her story of thinking she is doing the right thing.
I would agree with MrC, that maybe a small type of gift or random act towards her, might be the thing YOU need to do. Give you some relief. But do it with no expectation of her reacting nicely or even thanking you for it. Do it because you want to. We can't always stand by and feel like we are doing nothing.
Lift your heavy heart my friend and Choose Happy.
Always glad to hear from you PM. I did give her a framed picture of the cat and a book about gluten intolerance before I left. Actually, I left them for her in her work mailbox, no expectations. She has not acknowledged them or thanked me for them, but it felt good to leave them for her. I feel like the better person and I got to leave her with a positive before we went our separate ways for the holidays.
