Holy fucking shit. Grow a pair, go up to her, and ask her to go somewhere with you. If she's interested in you, she'll say yes.
Go up to her and ask, "Hey, you want to go to ____ right now?" It can be anywhere, go for a coffee or some shit. Point being when you make her face an immediate arrangement like that, she can't flake out on you later. She can say yes or no. If she says she has plans, even if it's an excuse, don't look disappointed. Just say alright and set up a meet for another time. If she does flake out on you a second time, she's not interested.
By the way, this is not a date. This is just to friends hanging out together. If she likes hanging out with you, you can escalate it from there. Don't act nervous or creepy, be confident and relaxed.