What do I do if I can't be with the girl I love?

I'm absolutely in love with my best friend. I would day to make her happy, and that's no exaggeration. She means the world to me, and the only thing I want is for her to be happy. I want to be with her so badly, but she only loves me in a platonic way. I'm her best friend, but she refuses to date me because she is afraid that it would be "too special". She said she felt like it would become to serious, and she isn't ready for that commitment. I don't want her to do anything she isn't comfortable with, but I really want to be with her. Am I being selfish? How do I show her that I can be a good boyfriend? Or, how do I get over my love for her?