Go talk to her first decent opportunity you get, soon as you're near her go straight in and strike up convo. Be cool about it, stay with your friends and try to stick to short convos, keep going back to your friends etc. Remember she is only worth a certain amount of your attention and she's gotta want to earn more. Main thing though, is be the coolest and funnest guy there, you're not out to pick up a girl you fancy, you're out to have a great time and you want everyone else to have a great time too. Good luck man!