Assuming it is you and your friends who are in trouble,(I`ll leave out what I think of waiting around while three other guys have sex with the girl before climbing on myself), a couple things that are important.
1) Did she know what she was getting into before you bought her there? If you bought her there, and suprised her with your friends you may very well have pushed her into it.
2) What did you talk about on the drive home? I`d say this is very important. If she wasn`t responsive, she probably felt very used, and if you did not tell her there would be 3 other guys, then you guys were very much in the wrong. And I can easily see a rape charge being brought against you.
3) This is a double standard in a sense. If this happend to a guy, I would have said he should not have let them pressure him into it. Call me sexist, but that`s the way I see it. The emotional state of a guy and a girl would be very different under the same situation.
4) If she was well aware of what she was getting into, and after the fact changed her mind. Then she`s really a b!tch. I wouldn`t have had anything to do with a girl who was willing to do this. But that is beside the point. Women who fasley accuse people of rape should suffer a VERY severe penelty. I`d say this is almost as bad as when a guy actually rapes a girl. The emotional and social damage that can be done is very real. Women should not be let off if they do this.