Best friend trying to ruin my chances with crush?

me & my BFF hav a crush on the same guy. we agreed that we'd b cool wid it and i am, but i dont think she is. every time she pes me a note about the guy she ends up giving wat i rote 2 him. all i do is try 2 stand by da guy often but she sits next 2 him, she giggles 4 no reason, and she twirls her hair a lot. now she hangs out wit dif. ppl and only talks 2 me when she's bored. i'd choose her over the guy any day but it seems as if she's trying 2 get me out of the pic. what should i do?