>>Just go up and admit I picked the project because I was interested in her?

That could go one of two ways: It could flatter her, or it could weird her out. If she was just a small interest you had or something, I would suggest doing it. However, you seem very unwilling to ruin a chance with this girl, so I would avoid most risks, if at all possible.

I would suggest just talking to her; have casual conversation. Don't be boring, but don't talk too much, either; just be cool.