Jines was born in Fairfax, Virginia. She began acting professionally at the age of 8. Her first television appearance was in 2000 in the episode “Demolition Derby” of the television series Third Watch as Lisa Hagonon. Her first role in film was as Harriet Deal in Drop Back Ten in 2000. She played Hannah Miller in the Law & Order: Special Victims Unit episode “Pixies” and Delilah in Gaudi Afternoon in 2001, and Jessica Trent in a CSI: Crime Scene Investigation episode called “Cats in the Cradle” in 2002. Also in 2002, she played Julie Morgan in Anna’s Dream. In 2003 she played Kristen Farrell in the television series That Was Then, and Rachel in the ER episode “A Saint in the City.” She was in Red Betsy as Jane Rounds, and played Demetra (A.K.A. The Deceiver) in Spy Kids 3-D: Game Over, which is the role that Jines is most famous for. In 2004, she guest starred on Jack & Bobby as Deena Greenberg in the episode “Today I Am a Man.” In 2005, she starred as Bridget Byrne in Silver Bells. Jines also had the recurring role of Heidi on The War at Home.

In 2015, Courtney won a fellowship with Sundance Institute’s Ignite Program, making her one of two female directors selected.