Mandy

Mandy is the rival of Clover, Sam and Alex at high school, when they are not on spy missions. Mandy's rivalry with Clover is the most pronounced. They often compete over boys, popularity contests, bragging rights, the latest fashions, and virtually everything else. Mandy will go out of her way to annoy the girls and get them in trouble, and will even use dishonest means in order to do it. Source: Totally Spies Wikia