My bent towards this would be the male protagonist refusing to marry her because she's a virgin. He doesn't want to get married only to find out she has no interest in sex or maybe he believes in the equality of sexes and since he is not a virgin, feels she should "test the waters" first.
The girl--being somewhat shy though attractive (think diamond in the rough)--confides to her girlfriend and so to make her more appealing, they shop for some sexy clothes and she gets a complete makeover.
Meanwhile the guy goes bar hopping with his buddies and confides his fears to his buddies, who were the main instigators in his thoughts about not fully tying the knot with a virgin and not knowing if she'll enjoy sex or not. After several drinks, he calls it a night and leaves.
As the buddies sit around and chat, in walks this incredibly sexy, sultry woman. They guy's best friend decides to hit on her, not recognizing her until he walks up to her at the bar...
The girl ends up sleeping with him, because she feels more comfortable with his friends than strangers, and finds out she loves, in fact CRAVES sex. Neither she or his best friend tell him about it, and she slowly branches out to the other friends, strangers, maybe even his boss or her teachers, becoming a sex fiend, enjoying "strange" too much and too often until SHE is the one holding off the wedding....
Now that I think about it, that might work, LOL...have to remember this storyline when I'm thinking of something new
