 Orphaned at a young age, she attended the Hamilton Aquatics Club, she won the Canadian National Springboard title in 1951, which was her first of nine titles in this event up to 1961, only failing to win it in 1953.MacDonald was selected for the 1952 Summer Olympics, but due to the lack of funding she was unable to attend, four years later she competed in Melbourne, at the 1956 Summer Olympics, in the 3 metre springboard, MacDonald finished the preliminary round of six dives in second place and so advanced to the final, in the final she did another four dives and finished in fifth but with all the scores combined she won the bronze medal.In Rome, at the 1960 Summer Olympics, MacDonald reached both finals, finishing sixth in the 3 metre springboard and she finished in ninth in the 10 metre platform.