BFF is being a jerk!??

I've known her since I was 2. She stayed at my house countless times. Well,anyway, she's been a snob and a jerk lately. Like, this guy (I liked at the time,I dont like him anymore) asked me to our school dance,he WAS my crush and he asked me to the dance so I was overjoyed if course,so I called her and she sed "Cool,I'm asking Bob (let's call her crush bob) tomorow" She asked bob and he sed no. One of her friends new I was going with him and that I was happy about she asked my friend why I was happy about and my friend sed "Shes just happy cause every other guy in school rejected her" When I didn't even ask any guy and SHE'S the one that got rejected!! I asked her why she sed that and she sed "Just be happy I didn't tell her you liked him" She's one grade above me and that grade had their prom (no other grade does) and I told her I liked this guy (not the one I went to the dance w/) and she asked him to prom! I sed "why the heck would you do that?!" she sed "Cause,i just wanted to go with him,gosh" This guy passed me a note in class and while we were passing notes I asked on the note "Are you goin to prom w/ (my friend)" and he sed "idk,I dont wanna go w/ her, but my sister would get mad if i didnt cause she's her bestfriend" And one guy sent my friend a message online asking her if she wanted to go to prom. She sed. "I said absolutely not,then I deleted him and clicked abuse,he's just so ugly" she's so mean and acts like she's to go good for anyone. What do I do?