What happens when two besties become full-blown worsties?

Avalon Greene rules the fashion scene at her sunny SoCal middle school with a diamond-clad fist, calling out classmates for their fashion-do's and most unfortunate clothes-pas. She's determined to host the social event of the season—a soiree in honor of her forever-friendship with Halley! Unfortunately, Halley's new look is one thing Avalon just can't celebrate. . . .

Halley Brandon is just back from art camp and can't wait to share her funky new style with her best friend, Avalon. But when Avalon cries fashion foul, Halley realizes her best friend's true colors may clash with her own. Has their ultra-fabulous friendship finally gone out of style?

From sharing custody of their puppy, Pucci, to drawing up a list of who gets which friends, Avalon and Halley discover what happens when you battle the person who knows everything about you—and isn't afraid to use your secrets to get what she wants.

Best friends. Worst enemies. Frenemies.