Sidney van der Hoff is Katie's best friends. The girls have been best friends since elementary school. Sidney is dating the high school football team quarterback, Dave Hollingsworth. Sidney is also one of the other contestants in the Quahog Festival Pageant.
Sidney is very name brand conscious, so she is always wearing the latest in name brand clothes and shoes and carrying a designer handbag. Sidney also loves to sing, so her talent for the pageant is singing.
Throughout the novel, Sidney fails to recognize Tommy Sullivan. Sidney keeps thinking he is a hot guy that Katie's brother met when he was at football camp. It's Sidney that catches Katie kissing Tommy in the parking lot of the Gull N Gulp and outside of the pageant tent. Even when Sidney finds out Tommy's true identity, she vows not to tell Katie's boyfriend.
