Gatien was born in Kamloops, British Columbia, Canada. She is of half German descent on her dad's side. She began performing at the age of four. She trained for a number of years in dance and musical theater. She was discovered at a model/talent convention and had a number of opportunities in Asia.
In 2009, Gatien played Mia Dearden in two episodes of Smallville. Her other television credits include Supernatural, Bionic Woman, Eureka, The Guard, and roles in the films In the Land of Women and Dr. Dolittle: Tail to the Chief.
In 2010, Gatien was cast as CJ Ward in the Cartoon Network live-action series Tower Prep. She was cast in The CW's 2012 pilot The Selection based on books written by Kiera Cass; however, the pilot was not picked up to series. In 2015 Gatien played the starring role of Jamie in the 1980s horror homage film Lost After Dark.