St-Georges made three appearances at the Canadian Junior Curling Championships in 2016, 2018 and 2019. In 2016, Team Quebec, skipped by her sister Laurie, finished the tournament with a 6–4 record, finishing in sixth place. In 2018, her team made it all the way to the final before losing to Nova Scotia's Kaitlyn Jones, earning the silver medal.[3] In 2019, her team lost to British Columbia's Sarah Daniels in a tiebreaker to qualify for the playoff round.[4] Cynthia skipped her own team at the 2019 Canadian U18 Curling Championships that season as well. Her team finished 3–3 after the round robin, just missing the playoffs. Also during the 2018–19 season, Team St-Georges lost in the final of the Curl Mesabi ClassicWorld Curling Tour event.[5]
Due to the COVID-19 pandemic in Quebec, the 2021 Quebec Scotties Tournament of Hearts was cancelled.[8] Since the defending champions, Team Noémie Verreault, had disbanded, Team St-Georges (the 2020 provincial runner-up) was invited to represent Quebec at the 2021 Scotties Tournament of Hearts, which they accepted.[9] The event was played in a bio-secure bubble in Calgary, Alberta to prevent the spread of the virus. At the Hearts, St-Georges and her teammates received a lot of media attention and fans thanks to their positive attitudes and strong play on the ice.[10] They also defeated multiple higher ranked teams in the tournament including the Wild Card team of Tracy Fleury (skipped by Chelsea Carey), Corryn Brown's British Columbia rink and Suzanne Birt's team out of Prince Edward Island. Ultimately, they finished the event with a 6–6 record and a seventh place finish.[11]
St-Georges is currently a health sciences student at Collège Montmorency. Her sister Laurie St-Georges is the skip of her team and her father Michel St-Georges is their coach.[2]