I am so sorry for the problems you're having, and also for the loss of your cat.
First, I should say that i was not abused by my parents as a kid, but my mother was. Badly, physically and emotionally - we are talking about abuse that would make the news. I've seen what it did to her, and how she has tried to deal with it. Unfortunately, the only way she could cope was to completely repress those memories - she has barely any memories of her childhood. So when my dad wanted us to go and stay with family (not knowing any of this background), she had no argument to stop it...
You remember the abuse. Whether your mother agrees with you or not, those are the memories you have, and they are valid. Whatever the provocation. And you seem to have turned out a decent person with a loving DH and extended family, so you can't have been that bad! Even if you were, what would you think of someone else behaving like that?
I don't know whether this is your 1st child, but do you really want her imposing her views of you on your kids? I'm assuming you wouldn't be letting your kids stay over with her, but if she is still in denial, she is not a good person for you or your family to be around. Quite apart from the stress you are under whilst pregnant!
My mum had very good counselling on the NHS. She didn't go into details with the GP, just said she needed to talk to someone about childhood abuse and could he please refer her, and did he mind if she didn't talk about it to him? (I just called and asked her, and she recommended taking cosmetic wipes with you so you can nip to the loo in the surgery and run repairs if it makes you cry and you feel self conscious. That's what she did). She is still dealing with it, but gets better all the time. She's accepted now that it was not her fault (the same blame games were played as you've had), and that she cannot fix her parents if they will not accept anything needs fixing.
I hope this is slightly helpful, and am aware that I am not a therapist or anything, but I can't watch this happening again and not say something. As other posters have said, she can find a hotel - she's an adult.
Good luck. And enjoy your baby when it comes - you will be a fab mum.