I feel like crap because I didn't do anything with her. I feel mad and sad.?

TALK TO HER. That's the only solution, keep an eye on her after class ends, then strike up a conversation. If she's with friends, start off with a question about the class so it seems more normal, then go from there. Ask for her number/email before the weeks up, definately, the worse she can say is no, but then you'll at least know you tried as hard as you could and didn't wimp out.