Ms Cassells, who works for H Samuel and turned 20 this year, bagged the Search For A Star title in 2009.
This year's winner will secure a meeting with top music industry figure heads at Mercury Music Group, the chance to record their own single courtesy of Imagesound, a VIP stay at the five-star Grosvenor Hotel in Park Lane, as well as live performances at Heathrow Terminal 5 and in House of Fraser's Oxford Street store window.