Aside from performing stand-up comedy, she has also appeared in several commercials, as well as on the television series ER, Law & Order, and 30 Rock. In June 2010 she was cast for the American cult series Dexter. She appeared in the television series Person of Interest episode Legacy, which aired on January 18, 2012, in which she played an attorney who had turned her life around after a checkered childhood.
She is known for her role in the 2007 drama Freedom Writers, in which she played Eva, based on real-life high school student Maria Reyes. Hernandez has said that she was “determined” to be cast in Freedom Writers. She admires Jennifer Lopez, and has stated that Lopez “opened the door for me so that I don’t have to take certain roles” as a Hispanic-American actress.