This is not my problem ?

[Moneyisanissue]

I’ve been NC with my mother for many many years. My eldest ds is 19. He knows this and he knows the reasons why.

unbeknown to me he had been seeing my mother , fine, he’s an adult so his choice. I only found out as she has written to me (!) because he had borrowed £500 off her towards his car insurance and has not paid her back as agreed. She is now saying o have to pay.

AIBU to ignore this or tell her it’s between them to sort out (as I’ve told ds)

"but he knew what she was like"

This isn't entirely true. He knew what your experience was and how you felt about dm. But I'm assuming that during his childhood he did not have much interaction with her to be able to accurately judge for himself. People find it very difficult to imagine how abusive others can be, unless they've personally been put through it. I bet your dm is horribly manipulative and ds is only a young adult.

You are right to keep insisting it is between them and to ignore her letter.

Try to see the positives.

DS now understands why you are NC and just how toxic his grandmother is.

Do not respond at all. Nothing.

I'd be fucking furious at my child for this.
But no, I wouldn't pay it.

NC is NC. Don't let her reel you in by contacting her to tell her to sort it with him.

Tell DS you want nothing to do with it and to deal with it as he sees fit.

And then move on.