Hey, she's 90 years ol...
I'd let it go, if you can..

I would have said "Thank you for the reminder, Mother. I will consider what you have said." and then let it go. It upsets you, she will never change or admit to wrong doing. Don't let her get a rise out of you, be as non committal and non confrontational as possible. Remember, they can't hurt you physically any more, and you can minimize the emotional hurt by disengaging. I am sorry you had such a crappy childhood, however you're stronger for it.

I had a horrible relationship with my mother all my life, but at the end of hers, she forgot about it all because of the increasing dementia. We still had some conflicts when I went to see her, but I let them slide. I figured, WTF, she's 96 and either doesn't remember or has completely revised our history, making any recitation of it pointless. I don't know how cognizant your mother is, but perhaps you should do the same.

Ask yourself if it would have done any good or helped the situation.

I call to keep in touch deliberately on non-holy days I can't make them notify me of illness and family deaths. ....with dozens of 3rd generation cousins great nieces/nephews it's further proof no person will be united in after life families populated by thousands we have never met centuries ago or centuries to come