Listen, if she brings it up, it's not because she wants to keep punishing you, it's because it's "unfinished business" and because she doesn't trust you, so she would want to get it resolved and see if should could trust again.
Cindy, they were not married and they were kids when it happened, but trust is trust is trust, whether it be friends, lovers, husband/wife, family. Once someone does an act of mistrust, they lose their credibility until proven otherwise.
I would say talk to her, see what she has to say. Let her bring up the past, tell her how you feel then ask her to let it go and get to know this "new you"
Live in the moment....not like you have to get into a relationship or get married.
Just all part of your journey my friend
Just have fun