That's really awful. I can't begin to imagine how you must feel. I think sometimes you have to be very specific with mothers about what they can and can't tell. I told my mum that I didn't want anyone to know about any of my pregnancies, m/c's or testing and she stuck to it. I bet she was dying to announce the latest pregnancy in her Xmas letter but she didn't as I'd told her not to tell anyone until we reached 12 weeks. Even now that we are past the "danger" period she's not telling anyone about the losses - just focusing on the future.

I'd suggest you email her, tell her exactly how you feel and then leave the ball in her court. If you don't get an apology I'd be keeping her at a distance and I certainly wouldn't tell her about the next pregnancy until it was well advanced (or your sister in case she told her).