Cox, a St. Croix native, moved with her family to Orlando, Florida, at age seven after spending five years of her youth studying dance in the U.S. Virgin Islands. In 1989, Cox was invited to participate in the Disney’s Magic Kingdom Christmas Spectacular. As a child actor, Cox appeared in Nickelodeon shows, including My Brother and Me, Kenan and Kel and All That.

Cox was a 1999 graduate of Dr. Phillips High School where she was enrolled in the Visual and Performing Arts magnet program for vocal performance. She earned a Bachelor of Music degree from Florida State University in 2003 after being accepted to their Musical Theater program. During her summers she worked at the Heritage Repertory Theater in Charlottesville, Virginia, where she played roles in Smokey Joe’s Cafe and Anything Goes one summer and performed as a recurring character in the Nickelodeon sitcom Noah Knows Best during another. Other regional theater credits include Rent, where she played club dancer and drug addict Mimi Márquez, the Chicago role of Liz, and Frenchie in Cabaret.

Prior to her role on Undercovers Cox made guest appearances on several television shows. In 2005, she appeared in CSI: NY, and Half & Half, and she appeared in One Tree Hill as Faith in season 3 episode 10 the following year. She also appeared in the marital crisis comedy Crazy, Stupid, Love., which was released in July 2011.

During the 2009 second season of 90210 she appeared in six episodes. She also appears in the fourth episode of season three (October 4, 2010). Her 20-something character, Sasha, becomes the controversial love interest of Tristan Wilds’ 17-year-old character, Dixon Wilson. The character is a DJ who met his character at a pizza parlor and a party she DJed on a yacht. Dixon led her to believe he was her age. One of the things that helped them bond despite his status as a high school junior was that they had the same cell phone ringtone. Eventually, Cox’s character lies about becoming pregnant to keep Dixon from breaking up with her.

On October 29, 2009, she was one of the This is It dancers who appeared on The Ellen DeGeneres Show to fulfill host Ellen DeGeneres’ birthday wish.

She appeared in all first-season episodes of Undercovers. She plays a character named Lizzy Gilliam, who is the sister of the female lead and who is unaware of her family’s involvement in Central Intelligence Agency activities. Originally, Jessica Parker Kennedy was cast in the role, but Cox replaced her in June 2010 before the first episode of the first season was aired in September 2010. Her character is described as “Boy crazy”. Cox says that Lizzy’s character, which spends much of her onscreen time running the family catering business, embodied much of her own true character and described the character as follows: “Lizzy’s a good character; very light-hearted, very fun loving, she’s got a good heart and an interesting past and she’s trying to deal with it”.

In 2016, Cox appeared in the Modern Family episode “The Cover-Up” . On August 23, 2016, Cox joined Chicago Med in a recurring role. She played Tiana, known as Sabine under the curse in Hyperion Heights in the seventh and final season of Once Upon a Time. In August 2017, Cox was promoted to a series regular. She appeared in 15 episodes of the season.

On April 28, 2018, Cox married Britt Leach. In December 2018, she gave birth to their daughter.

In 2019, she began co-starring in the second season of the ABC police procedural drama The Rookie as Detective Nyla Harper, first appearing in the fourth episode “Warriors and Guardians”.