O'Brien was crowned Miss Maryland Teen USA in 2006 held in late 2005. This was her second attempt at the title, as she had been a semi-finalist in the 2004 event. O'Brien represented Maryland in the Miss Teen USA 2006 competition broadcast live from Palm Springs, California in August 2006. She placed in the top ten of the nationally televised pageant, which was won by Katie Blair of Montana. This was Maryland's third consecutive placement in the pageant, the first time this has occurred.