Why does high school suck?

i was best friends with this girl till grade 11 ..we were separated by a girl who i tought was my friend when really her plan was to sobatage my life. now im in grade 12 and me and that same girl who broke me and my best friends' friendship hang around the same ppl...i hate her because shes always trying to put me down....i developped this attitude when she pisses me off i just give atittude to the rest of my friends...do you think it is a good idea to ignore all of them just because shes there?