How to write a story

The Arch Nemisis

Mean girls are mean we've all met one in our life time so its easy to sympathise!
Of course you mean girl needs to be a little exaggerated I mean how else will the reader understand that shes mean?!?
She NEEDS to target them for no apparent reason . But the reason must also secretly (or not so secretly to the clever readers ) about a boy.

Because promoting girls turning on each other over a guy is healthy!

The guy doesn't have to be the characters love interest but he must be in love with your character just like all the rest of the guys worth mentioning in your book! I mean shes irresistible how could they not all love her?

Your mean girl must be names something like Chelsea or Brittany or Paris because all girls with geological names are b¡tches it comes with the territory babe.

This girl doesn't HAVE to be the main enemy throughout I mean once your characters battled through an army of demons enslaved the devil and suffered without her daily Starbucks. Brittany's ,Paris's and Chelsea's  are a piece of cake.

But for the start its always good to see Chelsea/Brittany/Paris shove her into a locker at school just so we have a bit of immediate conflict, the way to describe these characters is make sure they are a harlot... I mean slut they need to have every guy on their tail or even better get the guys on their tail to shove your character into the locker and then say something witty like " thats from Brittany/Paris/Chelsea" .

Now we look at the big guns firstly the main 'bad guy' is always a guy because no lady could ever pull off something diabolical the Brittany's of the world work the bully streak out of themselves once they're out of their teens.
No these guys can look like anything you want as long as they have goons and laugh a lot thats pretty much it.