Stevens is of Portuguese descent on her mother's side and speaks Portuguese. She was instrumental in the creation of the Evan Gagnon Memorial Scholarship Fund, which gives college scholarships to the seniors of Pomperaug High School (Evan Gagnon, who died in January 2009 at the age of two, was the son of Stevens' Spanish teacher.) She was a member of Pomperaug High School's varsity swim team for four years. Stevens first performed for an audience at the age of five years, when she sang the national anthem at a party for a politician in her hometown.
On August 13, 2009, she auditioned for American Idol in Boston, Massachusetts and sang "At Last", where all four judges (including guest judge Victoria Beckham) advanced her to Hollywood. At the Boston audition, judge Kara DioGuardi called her one of the most talented 16-year-olds she had ever seen. In Hollywood, DioGuardi made the prediction, "You could be the potential winner." On March 24, 2010, Stevens landed in the bottom 3 during elimination night, along with Paige Miles and Tim Urban. She was proclaimed safe, giving her a spot on the American Idol summer tour.