The daughter of long-time employees of Southern California Edison Company, her parents enrolled Barr and her older sister in the before- and after-school care program of the Boys & Girls Clubs of Huntington Valley.

She was accepted to Chapman University's College of Performing Arts on the Dean's Scholarship, but left the school after a year to focus solely on her career.

[4] While still not yet in her teens, she appeared as the host of Encore Channel's Fear Fest: 31 Nights of Horror, as well as in television series such as Joan of Arcadia, Crossing Jordan, Drake & Josh, Zoey 101, and The Suite Life of Zack & Cody.

After her high school graduation in 2011, Barr starred in the dark comedy film God Bless America, her break out role.

This was followed by a major recurring role on the NBC series, Aquarius, starring David Duchovny, in which Barr portrayed the character Katie, who was based on real-life Manson Family member Patricia Krenwinkel.