Seriously though, people on here ARE socially-awkward to a big fault. Just talk to her, say she's the only person in the class you recognize, and that you want someone to sit next to and goof off a little with during boring lectures. Use that as an excuse to sit next to her and chat with her during class.
This comes from a person who literally is the most socially-awkward person on the planet. Please don't take this advice without having others who actually speak to other humans agree that it is a sensible action.