I kissed my ex bestfriend who has a girlfriendAnd I feel sooo bad about itWatch
Yes you lied, which is not good at all, but you seem like you’ve acknowledged what you did was wrong which means you will be less likely to do it again.
But if you still feel like it’s bothering you - you could just tell her since he’s not with her anymore. You could say ”Actually I just remembered that..”
then go from there.