Shelby Rose Cummings is one the main Antagonists in the movie, and is the most popular girl in Sam's school and the Captain of the cheerleading squad. Shelby is the mean girl in the series and do anything to make Sam’s life a living hell. She is a little annoyed by Sam's stepsisters Brianna and Gabriella, but tolerates them because they gave her a Prada bag for her birthday. Her best friends are Madison and Caitlyn. Shelby torments Sam and calls her "Diner Girl". She used to be Austin Ames's girlfriend and manipulated him into doing what she wants, but he dumped her before the Homecoming Dance. When Brianna and Gabriella lied to Shelby by saying Sam tried to steal Austin and show her Sam and Austin's emails, she immediately becomes jealous. When Shelby and the stepsisters expose Sam's secret and humiliate her in front of the whole school during the pep rally, she's delighted by the chance to get back together with Austin but he ignores her and keeps his distance from her. At the homecoming game, Shelby gets her comeuppance as Austin hugs and kisses Sam and Shelby becomes sad. At the end of the movie, she tries winning Carter, after he is seen in an acne commercial and is popular but dumps her for another girl, after seeing her true colors from when she humiliated his best friend Sam.