Approach her outright

You go up to Tiffany while she's making an ass of herself, trying to impress some Kappa Sigma crew rowers. It's maybe not an ideal time, as one of the guys is cracking jokes and Tiffany is giggling like an idiot.

It's the frat boys who notice you before Tiffany, and they are none too happy about it.

"Yo, you know this is a closed event, right, bro?" One of the alphas tries to assert dominance immediately and close you out. He's right though, aside from their frat and the Delta Delta sorority sisters, this party is off-limits.

"Hey, hey," the guy cracking jokes to Tiffany is the one with a cooler approach. "I mean, my broski is right, but maybe you're one of the girls' boyfriends?" He's giving you an option to introduce yourself, but there's hostility behind the friendly demeanor.

Tiffany finally notices you. It's not the first impression you wanted to make, being grilled by boys she's flinging herself at. Markedly younger than you, Tiffany shies away, closer to the frat bros.

"Or maybe you're, like, working the party? Serving the drinks?"