When she was 19, after graduating from Valley High School in Albuquerque, NM, Kelly returned to Los Angeles. While on a test shoot for a modeling agency, she was approached by a former Playboy Playmate interested in managing her, and who placed Kelly as a receptionist at a surgeon's office who would provide Kelly breast augmentation in exchange for hours worked. She ultimately decided against the procedure, leading to her being fired. However, the exposure to the medical field prompted her to attend school for a year to become a surgeon's assistant; afterward, she worked as a scrub tech. She spent four years in that vocation while also auditioning as an actress before landing the new NBC television drama Friday Night Lights, based on the high school football movie of that name. In the interim, she had small roles in movies and shows, including the film State's Evidence, and a recurring guest role on the TV sitcom What I Like About You.
She shot a cameo for The Kingdom, alongside Jamie Foxx. Peter Berg, the creator and pilot director of Friday Night Lights, directed the film. Kelly was the lead actor on The CW's 2009 pilot Body Politic, which did not go to series. Kelly was a member of the ensemble quartet that starred in the CBS comedy pilot Mad Love, playing Kate, a Midwestern girl who falls in love with Henry at the top of the Empire State Building, but was replaced by Sarah Chalke.