At the Tokyo 2020 Olympic Trials, Bellio won gold in the 1,500-m freestyle and captured silver in the 800-m freestyle. Her performance in the 1,500-m freestyle qualified her for her first Olympic Games at the age of 16.
At the 2019 FINA World Junior Championships in Budapest, Bellio was a member of the 4×200-m freestyle relay that brought home bronze. Individually, Bellio finished 8th in the 200-m freestyle, 14th in the 1,500-m freestyle and 15th in the 800-m freestyle.
At the 2019 Canadian Swimming Championships, Bellio won gold in the 400-m, 800-m, 1500-m freestyle and the 400-m individual medley.
At the 2019 Canadian Swimming Trials, Bellio finished fourth in the 800-m and 1500-m freestyle. Bellio also finished seventh in the 400-m freestyle and the 400-m individual medley. She achieved personal best times in all her events.