She was born in Vancouver, British Columbia on September 12, 1992.
At the age of seven, Fast wrote, directed, and starred in a short film entitled The Red Bridge. She starred in her first feature film, Fido, at the age of 11 after gaining her first agent. She also appeared in television films such as His and Her Christmas, Past Tense, and Firestorm: The Last Stand at Yellowstone. After she starred in Fido, she appeared in TV series until 2009, when she starred as Julie in the feature film Helen.
Fast played a role in Hungry Hills and Repeaters, both of which premiered at the Toronto Film Festival. In 2010, she had a leading role in Triple Dog. Shortly after, she shot her most recent episode of Supernatural and featured in Last Kind Words and Blackbird. In 2012, she had a supporting role in the film Jack Reacher.
Fast won two Leo Awards, the first one 2007 in the category Best Lead Performance by a Female in a Feature Length Drama for her role in Past Tense, and 2011 in the category Best Supporting Performance by a Female in a Feature Length Drama for Repeaters.
- She was born on the same day that Anthony Perkins died.