The 14-year-old Australian saved her best for last, delivering a gutsy and precise performance on her third and final run and was rewarded with a huge score of 93.18 on a sun-soaked day at La Concorde.
Japan's Cocona Hiraki won silver and Britain's Brown took bronze. Hiraki also won silver and Brown bronze at the competition at the Tokyo Games three years ago.
A new champion was guaranteed after Tokyo gold medalist Sakura Yosozumi failed to qualify for the final during preliminary rounds, which were held earlier in the day.
