I wouldn't worry about it. I mean, hey, if your girl says that you've got a nice smile, then what have you got to worry about??
I suppose that you could consider getting braces, but thats up to you. Ask her about it too, and see what her opinion is on the idea. The amount of time that they're on can vary greatly. I knew someone who had them on for QUITE a few years! But you could get lucky...you never know.