The 2004 movie "Mean Girls," starring Lindsay Lohan as a girl negotiating the jungles of teenage subcultures, put a new label on this type of teen.
High heels, short skirts -- whatever the latest fashion is, they're into it. They form exclusive cliques, and gossip is their native language. In your day, they might have been known as Valley Girls or Barbies.
Mean girls crave popularity, often because they feel insecure. Yet they have a hard time with genuine relationships. They cultivate "frenemies," which are girls they hang with but secretly hate. Even their BFFs (best friends forever) might be spurned tomorrow.
The name points toward what you should watch for. Petty gossiping is one thing, but real, verbal bullying can be destructive.