Are you good at being funny/humorous??

Just introduce yourself, say you don't know anyone in the class, and out of everyone she seemed like the most interesting person to get to know. Start general conversation... if she's playful, tease her about something, and while in the joking moment say "I better stop teasin you.. I don't want your boyfriend to come lookin for me" with a smile.

You only feel ackward because you haven't broke the ice yet. And don't think like that.. don't think "I have three more years around her" because you never know what is gonna happen tomorrow. She could transfer, she could meet a guy who she's gonna date for the next year and a half... it's better to make the effort to get to know her ASAP.