You mention having "limited contact." I think that's going to have to be your game plan right there. What she's doing is awful and, like you said, it's behavior that you would not tolerate in anyone other than her. I don't think there is anyway that it's not going to bother you. We all crave parental approval for as long as we and they are alive. She's foolish because she will eventually need you more than you will need her.

You have every right to terminate any conversation or visit where you are being the target for "pot shots." It might be best to try and do that in a business-like fashion without any emotional display on your part. (Very hard to pull off, I know.) At some level, she kind of gets a kick out of reducing you to an upset mess of emotion. Don't give her the satisfaction. If you visit her, just say, "Well, I'll be running along now, Mom. I've got so much to get done today and tomorrow." Same line can serve the same purpose on the phone. And avoid emailing her to express anything because, as you are finding out, you get absolutely nowhere with that. Just disengage when the pot shots start. That's so easy for me to recommend and hard for you to pull off.

I had a father kind of like that, though not as bad. I tended to become very upset, which never did me any good. It's kind of like dealing with a child who uses obnoxious behavior to get attention or show defiance. The last thing they want is to be ignored. So that's the best thing to do, along with removing yourself from their presence. You have some hope of training your mother to realize that, you won't be there, if she starts her nonsense. But she will always test you and push that envelope just as far as she can. I feel for you.