And girls will not let minor things go and their reactions are so out of line with the situation. Outrageous reactions to the smallest things. And it always, always, comes down to boys and clothes.
They can be vicious. I have seen girls spread hurtful (and very damaging) rumors and create myspace pages that I think are just hateful, all over some girl getting a boy that another girl likes. I've known a girl to get her teeth knocked out (yes, her front teeth!) over accidentally staining another girl's shirt. And I have most certainly seen teenage girls ostracize another girl over the tiniest of things.
Girls in groups are the worst. They can be plain evil!