Courtney was born in Fairfax, Virginia. She began acting professionally at the age of 6. 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 (2000) and Hannah Miller in the Law & Order: Special Victims Unit episode "Pixies" in 2001. She played Delilah in Gaudi Afternoon (2001) and Jessica Trent in the CSI: Crime Scene Investigation episode called "Cats in the Cradle" in 2002. 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 Courtney is most famous for. In 2004, she guest starred on Jack & Bobby is Deena Greenberg in the episode "Today I Am a Man." In 2005, she starred as Bridget Byrne in Silver Bells and Amanda Wilkinson in Because of Winn-Dixie. Courtney showed her flair for comedic acting in her recurring role of Heidi, on The War at Home.