Cut her out. She doesn't deserve you. She is a malicious vindictive bigot. I cut my relatives out, and it was one of the best decisions I've ever made. But I cut out every last person I even shared the slightest bit of DNA with. Bigotry doesn't even begin to describe my relatives.
I know it can be difficult for people to accept and adjust to someone in their family being transgender, but there is no excuse on earth to justify what she has done, and is still doing.
If she asks, just tell her she is not worthy of your time. "Kiss my ass" is a good reply to her, in my opinion.
And like many others here, I also grew up in an abusive environment, from all people around me, including blood relatives. My father enjoyed knocking me around, my mother enjoyed telling me that I was basically a "curse on the world since the day she made me". My uncles and cousins went out of their way to belittle me as much as possible and treat me as subhuman. I remember one day we were hauling hay. Afterwards, my cousin and his friend got paid $50 each. He tried to give me $5. I just kicked him square in the nuts and took his wallet. I ended up having to crack my cousin and his friend in the head with a stick, but showed them that they weren't going to pull that kind of (expletive deleted) with me.
But that was the light stuff. There were several times my life was in danger due to my relatives. Now I speak to no one. My parents are, thankfully, dead now, and I don't miss them one bit. As it sits, no one knows where I live, what my phone number is, and what my email is, and it's going to stay that way. If, by some stroke of misfortune, I run into them at some point, there's a chance all hell will break loose. If I can get away with it, I'll pretend I've never met them before. But I'm sure at least my sister would press her luck.
It's not that I don't have the patience or tolerance for people like that, it's that I won't have the patience or tolerance. In my eyes, they are beneath me, and always will be. That's a very conceited statement I know, but it's not going to change. I'm not willing to change it.
So do what you have to do. It may hurt, assuming you care about her, but it's the lesser of two evils.