My only friend has changed completely?!?

So I'm going to become an upcoming freshman this school and I'm going to a completely new high school. I only know this one friend of mine that'll be there. We used to be close, but since she's at a diff middle school we became distant, but now we're talking and stuff again. Nowadays, she's turned into a totally different person and changed, she's pissed all the time and bitchy. Because she'll be the only friend I have at my new school, she'll be the only one I can depend on, but I really can't stand her bitchyness nowadays, any help? :[