Grenier comes from a French-speaking region in eastern Ontario. She learned to ski on Mont Tremblant in Québec . In her youth she was a talented water skier and became Canadian Junior Champion in 2012, but then decided to focus on alpine skiing. She contested her first FIS races as a 15-year-old in December 2011, and in January 2012 she achieved her first victory at this level. In March 2012, she started in the Nor-Am Cup for the first time and immediately finished in the points. As a result, she established herself in this racing series in the front midfield. On December 15, 2014, she won her first race in the Nor-Am Cup, a Super-G in Panorama .
Grenier made her debut in the World Cup on December 7, 2014 in Lake Louise , where she finished 32nd in the Super-G. On January 25, 2015, she won World Cup points for the first time with a surprising 13th place in the Super G in St. Moritz . At the 2015 Junior World Championships in Hafjell , she won the bronze medal in the giant slalom. A year later in Sochi she won the gold in the downhill and silver in the super-G.
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