Heinz competed in the 1951 Pan American Games at the age of 15, winning the bronze medal in the 100 metres and the 4 x 100 metres relay. A year later Heinz competed in the 1952 Summer Olympics in Helsinki, Finland. She ran in the 100 metres and finished third in her first round heat, eliminating her from the competition. Just days later she took part in the 200 metres, again being eliminated at the heat stage after finishing fourth. Her final event in the Olympics was the 4 x 100 metres relay with teammates Lilian Buglia, Gladys Erbetta and Ana María Fontán. The team finished in third place behind Australia and the Netherlands and so did not progress to the final.