As a woman & a person who pledged a Sorority in college (went to 100's of fraternity parties) I can see why you might be concerned. There are key factors OTHER than your insecurity about her wanting to party it up again, and possibly cheat. 1st there will be guys there, and tons of men drinking, can be unsafe. At several of the TG parties there were ABX girls that would get drunk and pass out, and several of my friends saw the guys carry these girls up to rooms. I personally avoided that house for that 'said' reason. A girl can easily have something slipped in her drink & whether or not her intentions were for bad things to happen, they can. The best advice if, you're going to put yourself in those situations, is to go with a group. NEVER go alone, go with at least 2 other girls, and NEVER leave the room without the other 2 knowing who you're with and where you're going. This may seem like an over reaction, BUT if you're there to have fun, theres no reason you can't do it safely! Don't drink ANYTHING that you didn't see poured. NEVER set your drink down, if you do, don't drink it, get a new one. Don't let a guy offer to hold your drink while you dance, etc.
As her bf, the best you can do is trust her, trust her judgement, and trust that she's really just gonna go have fun & not try to hook up with anyone else. BUT in the event that she does, its not your fault and its best to find out her level of maturity, honesty, and integrity as soon as possible. It seems like you have some serious trust issues, whether she cheats or not, plans to or won't, you need to learn to give her a little rope... she'll either show you that she's trustworthy & someone who deserves your interest or she'll hang herself with it. Not much you can do, but wait.
good luck.