I think I'm in love with my best friend?!?

I would suggest writing an anonymous letter to her. Maybe she isn't really as in to him as you think she is. You can make a different email than the one you are using, and email her through that. She might email you back asking who you are and stuff like that, but you can always add another paragraph or something really sweet, and by the time she figures out who you are, she will already think of you differently (in a good way)