Shanahan grew up in the Taranaki village of Lepperton and attended New Plymouth Girls' High School.
She also made appearances in television shows The Insiders Guide to Happiness, and Outrageous Fortune.
[3] In 2008, she starred in the film, Second Hand Wedding alongside Patrick Wilson, Ryan O'Kane, and Geraldine Brophy.
[5][6] In 2011, she played Detective Constable Caroline Derwent in the mini-series, Underbelly NZ: Land of the Long Green Cloud, which was based on the criminal career of New Zealand drug trafficker Marty Johnstone.
[8] She relaunched the West Coast Youth Theatre in 2014 as a way to help young actors enter the arts.