Iz...
what is important now is that, when your daughter told you about this,
you didn't duck it
you didn't try to find a way to blame her for it
you didn't insist that it never happened
you didn't change the subject
you didn't get angry at her for bringing up the past
you didn't misinterpret what she said and give her heck over that misinterpreted version.
what you did instead was...
sit with it...
believe her about it...
make an effort to remember it...
make an effort to 'own' your part of it...
I am not saying you were, or did, wrong... I'm saying you were willing to consider that you might have made a mistake...
Iz, it's so valuable to your daughter now that you can even THINK that you MIGHT have made a mistake then. If you can believe me about this, THAT may be more valuable, your ability to do this, and her seeing your ability to do it, than if you'd never made any mistakes with her ever.
A parent who can admit imperfections is so valuable... because we are all imperfect...
Hugs and flowers for you for mother's day. You are an admirable, brave mother, Iz. Truly.