thats the perfect situation, you wont see her after 3 weeks, so what have you got to lose? You have 3 weeks to show your presence, and on the last day grab her number.
If she says "no thank you", just say "the pleasure was all mine", walk out and you'll never see her scales again.
You guys are taking the same class together, you have so much to discuss, stop trying to find the perfect moment to strike up a conversation, because either you'll miss the chance,
or some other dude will take her.
But if you enjoy being creepy and watching from the side then coming here and posting on TM3 about your issues... thats great too.