First of all, don't tell your girlfriend what to do! Sure way to lose her! If she's interested in a classmate, let her see what it's all about! In the meantime, be there for her - be supportive - be a great friend! When she gets over her crush, she'll realize how important you are to her! If you care for her - give her space - she's very young! If you are too controlling, you will drive her away! Be patient!