I would tell my parents to keep their thoughts behind close doors and to always greet her with kindness, dignity and respect. If they cannot do this, then I will no longer communicate with them.
I expect the same thing from my future wife. So whoever acts childish is the one I will cut loose. Whoever gives me an ultimatum is the one who loses.
My aunt is probably one of the worst people you could possible know. She was so rude to my oldest cousins girlfriend, who he had a child with. Not going to go into detail but one day he had enough, picked up his baby, grabbed his girlfriends hand and left and never came back. I still talk to him so he didn't leave the entire family just excommunicated his mom - she has not seen her granddaughter in 10 years and also now has a grandson who is 4. That is the price you pay when you push your child too far.
My aunt is also horrible rude to her second child's husband. I have no idea why this cousin hasn't left yet but my aunt is straight up terrible to her husband, for no reason.
Her youngest son? She already pushed him out, he just joined the military so he can be gone once he graduates. His mom is comparing him to his older brother and that he will just leave her too. He told her of course not but he told me in confidence, that he is going to the military so he can get away from her because she is also horribly rude to his girlfriend.
I just watch in amusement as she chases all her children away and to never see her grandkids because of it.
So, I totally support them for excommunicating my aunt for their wife, husband, girlfriends, etc. If your parents suck, then do what makes you happy. Warn your parents and tell them that the situation they cause may be irreversible for them. That is the person you love and they need to deal with it and be happy for you.