Is she giving you any other signs that she doesn't like spending imprtant time with you? If not, then don't worry about, go have a ball with all of your old buds without worrying about your GF for one night.
If you are getting other signs from your GF, then dump her and bring some hottie in a short mini skirt with big bazoongas who likes to bang and fish.
(not sure where 'clams was going with his reference to mini-skirt. My mentioning of mini skirt in my post is only coincidental and not related to 'clams' reference, unless it is the exact same thought)