It would be nice if that happen to me, ha ha. Just kidding, anyhow. Ask her out, sure. It's kinda mean to ur BestFriend so tell him like, i'm gonna ask her out for the dance, I know u like her but i hope u respect my decision. Hope he does. This is not a good answer but it's the best i could think of. Even though u didn't like this, i hope u still respect it.