I've found there is a difference between pretending it didn't happen, and letting it go. Pretending is harmful and letting go is freeing. I have been able to let go a lot of things, but never forget they happened and who really was to blame.

I don't think it's necessary to tell your mother anything more. If you have a decent relationship with her now, I'd concentrate on that. Possibly hurting her feelings or guilt would not help you or her at all right now.

I hope things keep getting better for you and her.