Ok need advice my bff likes this guy but?

ok i got a hugh crush on my bff,and she know how i feel about her,but she always be around some guy all the time and talking to him and hugging him and horsing around and what not,she really likes this guy.but the problem is the guy has a gf and he is playful with all the girls.i just dont want her to be used in his game what should i do