Doubleday was born and raised in Los Angeles, the daughter of Frank Doubleday and Christina Hart. She grew up in a show business family: Her parents are former professional actors, and her younger sister Portia, is an actress as well. Her mother currently works in the entertainment industry as a playwright and also as a producer in the theater. She attended the Music Academy at Hamilton High School in Los Angeles. She had a number of supporting film roles in her early career, and in 2015 began starring as Rhonda Lyon in the Fox musical prime time soap opera, Empire.
Doubleday made her acting debut in an episode of the CBS procedural Without a Trace in 2002, and in the same year appeared in the feature film Catch Me If You Can. She graduated to supporting roles in films Waiting... (2005), The TV Set (2006) and Accepted (2006). In 2007, she held the female lead role in the ABC comedy series, Cavemen. In the following years, Doubleday continued performing on television, with small parts on CSI: Miami, Brothers & Sisters, Bones, The Closer, Criminal Minds, Drop Dead Diva and Witches of East End. Doubleday also performed in the recurring role of Logan Louis in the HBO comedy series, Hung in 2011.
Also in 2015, she was cast in the independent drama film, Po directed by John Asher, about a single father raising a son with autism. Doubleday also appeared as a celebrity guest on The CW improvisational comedy show Whose Line Is It Anyway, in June of 2016.
Early 2017 she featured in the popular horror series "Scary Endings" alongside Australian actor Adam J. Yeend in an episode called 'The Water Rises'.