What advice should I give to my BFF about the guy who likes her?

there is a guy in my school who (supposedly) likes my friend. His friend told my BFF that he is going to ask her to the dance, and my BFF doesn't particularly like him. (she likes someone else not in the school) In my school we HAVE to dance with anyone who asks us (long story). he has asked many girls to the dance. ALSO he always says hi or sup, but he says that to everyone, and she always blushes.she always asks me for advice, but idk what to say (AND I DO NOT LIKE HIM)! does he really like her or is he just playing with her head?!? please help!!!