Is she a relatively open-minded person? It's all about her personality. You should make sure that she would be okay with that knowledge, or even hints.

Even better, look for signs that show that she might be interested in you, too. In your best friend position, you're much closer than you would be if you were just this ordinary guy passing by, so I think you have a good chance of changing your friend status to he's-my-best-friend-but-I'm-starting-to-like-him.

Don't tell her yet. Maximize your chances. Good luck!