I became friends with a girl that was a b word when i was about 12... very little parent supervision.
She made other girls lives miserable in school because they werent as "cool as us."
Also, Because of her I had my first encounter with beer, ciggarettes and weed! At 12! THat;s insane!

Just remind her.... once high school hits they're not the big kids anymore.... they are the babies.
And older kids arent going to put up with b words!

U could just THREATEN to send your daughter to another high school? Say if this is the type of person she's going to become from hanging out with (L) then you need to act NOW and get her away from her before it gets worse.
Even if that means travelling an hour by herself, and not knowing anybody at the other school!
That's what i'd try. But..... i'm a mean, hard a$$. =P