Answer:
Ok, I don't suggest going to the friend you two have in common because of course the girl will run to the one that you're interested in and tell her.. It's girl code. That's how we are, esp if we know someone likes one of our friends!(It's exciting to talk about haha)
So I suggest adding her on facebook and just casually talking to her throughout the winter break. Don't try to fb chat with her everytime she signs on or anything creepy... but once she has accepted you, leave her a comment about the dance just making a joke of it(like the things you quoted on your clearer description about looking down at someone's feet or w/e). See where it goes. If she talked to you more than the guy you traded off with then that IS good, in your defense...but then again dancing with a guy that you just met on one night of your life doesn't really seal the deal for you...
Start talking to her. Be playful and if you two continue to talk back and forth for a few days see if she wants to hang out and do something?(mall, a movie, or w/e wouldn't be "too ackward".)