You should do some thinking about what sex means to you, and ask her to do the same.
If I were in her shoes, I would be very bothered by your worries, because it seems like you're questioning what kind of person she is, what she'd do if she could get away with it. Maybe that's not quite explaining it right-
A friend of mine occasionally annoys me by making comments that seem to assume I'd like to go around screwing a bunch of random guys. Not that there's anything wrong with that, I know he enjoys casual sex and would like more opportunities in that area, and envies me because if I wanted to, I could have oodles of casual sex- the reason I get annoyed is that his comments make me feel like he just doesn't understand me--which, considering the amount of time we've spent talking about sex and relationships, and that I've explained to him many times that I get emotionally attached to people I have sex with, and that sex without some kind of emotional intimacy just doesn't interest me, his lack of understanding makes me suspect he's a total idiot or he just doesn't listen to me.