Thorne's first film appearance was an uncredited role as a sidelines fan in the 2003 film Stuck on You. She has since appeared in film and television projects including Entourage and The O. C. as a younger version of Taylor Townsend. In 2007, she joined the recurring cast of Dirty Sexy Money's second season, her first major television role. She played Margaux Darling. The series revolves around lawyer and family man Nick George when Nick's father mysteriously dies in a plane crash, he agrees to take his position as the Darling family's lawyer, while trying to discover who committed the murder. In 2008, Thorne starred alongside Christian Slater and Taylor Lautner in the short-lived drama series My Own Worst Enemy, for which she won a Young Artist's Award for her portrayal of the character Ruthy Spivey; Thorne described her Enemy casting as a major breakthrough as this was the first recurring role in her career. That same year, she starred in the third-last episode of October Road as Angela Ferilli, the pre-adolescence crush of the main characters. Her older brother Remy also guest-starred in the same episode as a younger Eddie Latekka.