Wait till you are quite a bit bigger and find a way to fuck her by letting her know you have a big dick (inderectly of course)... trust me, if you can some how mess with her head, then most girls tend to forget what they thought before as long as they feel like the current situation is what they are into.... they are naive.
After you fuck her, act like she was just another ho and get yourself another girl... this will really fuck with her head...and because you or her never mentioned anything about a relationship, then she might still try to get back with you and try to get you into a relationship (because she's scandulous). Act a little interested then back off like your not interested...like she's just another ho and she's not important to you.
Because she got you to act interested, then she will try to get that "power" back (when you back'd off) by acting even more "interested" (because scandulous woman are insecure and they can't stand to get turned down). Keep acting interested and disintrested (making her wonder what's going on and stirring her emotions) over and over, looping the string, until she goes crazy/obsessed.........and then fuck her best friend and say it was because she was too loose.
A little pscyhological trick I picked up from a book that my friend let me borrow, that work's absolutly wonderful... He's actually a stripper so he dated all kind's of scandulous women and I've learned alot from this guy.
Good Luck