well since this girl ain't a big deal, try the following, but only if you got BIG BALLS:
after you nail her, while you are still lying there (and you are sure she's come at least once) say to her
"you know, I'm kind of new at this. I was wondering if you'd like to be my sex practice partner. You know I'm a model, so I'll probably be dating a lot of girls, so I can't promise you there's any hope of a relationship. But if your up for it, we can try out lots of freaky sex. If you're not, I totally understand. I'm mean I think you're cool and everything, I totally respect you. Your call. Whatta ya think?"
or words to that effect.
I am suggesting this predicated on you saying she was ok with "only" sex.
Of course you could do this anyways and not say anything. But if you DID say the above, that would satisfy any moral issues you may have.