you cant think that every situation will end the same way it ended for you and your ex 15yo gf. People are different. Your gf could have been in a church, virgin, and you could have been her 1st boyfriend ever and be a good man for her, and she end up cheating on you later on because she wanted to enjoy other dicks. That is how life works. You are still an unexperienced man as I can see. I had many relationships, "bad girls" who wanted to be loved and would give anything for that even if to the world and to herself she would tell otherwise. And "good ones", who turned into a total bitch and desiring for an open relationship, because she wanted to experience more than one dick. And be crazier and less mature than, the ones people would call slut, but once she had someone to care for them and be that guy they could trust, be more trustworthy, reliable, affectionate than any other women, besides being goddess on bed and doing everything to please you.
I will never say "she won't change", "this will never happen". Because people are very different. We know nothing. This is me talking about real life, but Being a Dik is a fantasy world. And lets say, if DPC has a fantasy of a bad girl turning into the best lovable girfriend in the world, he can do so. It is his story after all. Even if he doesn't, Quinn is still my favorite character and depending on where this story lead us, I will be with her untill the end.