Help with friends please?

I have one friend who has been consistently rude and mean to another friend and I for years. This year we decided not to be friends with the mean girl anymore. The mean girl got mad and got a gang together who now hates us and is getting everyone else to hate us. My other nice friend got insanely pissed and send a nasty txt to the mean girl. The mean girl now says she's "depressed" and "crying everyday" and threatening to take us to guidance. If we go to guidance my friend and I will surely get suspended for cyber bullying (I didn't even do anything THAT bad, but I'm an "accomplice" I suppose) and my parents will ground me for life. Is this fair at all???