With some people (ESPECIALLY family, and especially parents or siblings) there are just certain beliefs that are not going to change (at least not on account of anything YOU do or say), and thus certain topics that you simply can't constructively discuss.
So, don't. Just don't.
Any time she brings it up, politely thank her and change the subject, preferably to some sort of topic she enjoys as much or more. EVERY time. It takes two to have a conversation
If she calls you on it ("every time I try to say something to help you out about <whatever> you change the subject and won't talk about it") tell her that you just don't seem to be going to see eye to eye about it, and you'd rather talk about something else and enjoy each other's company without stressing each other out. Then just continue to not be willing to discuss it.
If she is like my mom, she will never really quit bringing it up
, but you can at least avoid getting dragged thru it all, over and over and over again, and making you stressed-out and crazy
Good luck,
Pat
So, don't. Just don't.
Any time she brings it up, politely thank her and change the subject, preferably to some sort of topic she enjoys as much or more. EVERY time. It takes two to have a conversation

If she is like my mom, she will never really quit bringing it up


Good luck,
Pat