St-Gelais was a member of the Canadian team that attended the 2010 Winter Olympics in both the 500m and 3,000m relay. Prior to these Olympic games she had yet to win any medals at an Olympics or world championships. On February 17, her 20th birthday, she won a silver medal in the 500 metres. She followed this success with a silver medal on February 24, in the 3,000 metre relay, along with Jessica Gregg, Kalyna Roberge and Tania Vicent. After the Olympics St-Gelais continued on her success at the Olympics with a bronze in the 500m at the 2010 World Championships as well as a silver in the 3,000m relay. At the World Team Championships St-Gelais was a part of the Canadian squad that won silver in the event. This concluded what was the most successful season of her young career, with 2 Olympic silvers, 2 world championship silvers, and a worlds bronze.