This scenario is rich with themes, characters, all sorts of possibilities.
Sorry, Bald J&F--I dig rape stories. I also love victims who are true victims. That's just my little sickness--but I emphasize in various posts: if you're not role-playing with an agreed-upon script or setting, this had better be just plain old fantasy!! Check out my response to "Kelsey" on the posting "Fantasy Rape with Older Men" at http://www.about-rape.com/bbs/index.php --an alleged "13-year-old" who wants to be raped.
Yeah, right.
That said, I would cast the victim as the 16-17-year old daughter of a corrupt, evil tycoon. It's her birthday or coming-out-party, and she's being displayed by the old man as "fresh meat" to entice the sons of other tycoons, hoping to advance a business alliance.
THEN you have her enticed away from the party. Maybe an anteroom, where some kind of coercion (blackmail, business extortion maybe) is used to make her comply. As always, I say: lots of silk, yards of petticoat--throw her on her back (maybe on a settee), push her skirts up, and rip off her dainty silky pantaloons (if it's a period piece).
Then there's something to be said for dragging her down to the wine cellar, and hanging her from a ceiling hook in the chilly, dim, chamber, where nobody can hear her scream!
Another variation: have a young revolutionary (or cadre) abduct her at this wonderful moment of feminine & aristocratic prominence, and throw her into a car trunk (or across a horse) and whisk her away to the rebels hide-out, where she gets raped and converted to cause, Patty Hearst style. It could work as a gang-bang, or she becomes the leader's personal sex-toy, as with a pirate captain. By utilizing the "Stockholm Syndrom," Bald J&F, in which captives come to identify with and bond with their captors, you could work this into a rape, becoming 'reluctance,' leading to willingness" plot, although I, for one, don't usually like those.
After all, if the girl's going to be raped, make it a bonafide crime!