The 19-year-old former figure skater, who led the way in qualifying and so started last, scored an imposing 94.20 and was able to celebrate her victory before coasting through her final run.
Devin Logan of the United States claimed silver, while Kim Lamarre took bronze for Canada with her second run after being one of several skiers to fall on her first.
Canadian Yuki Tsubota appeared to suffer a serious injury on her second run.
Canadian favourite Kaya Turski had earlier fallen on both of her runs in qualifying, while German World Cup leader Lisa Zimmermann also failed to make the final.
A seven-times X-Games champion in the event, Turski fell heavily on her first run and was unable to do any better on her second, failing to nail a jump and crashing skis first into the snow.