The 17-year-old clocked 84.51s on Saturday with France’s Tess Ledeux in second and Italy’s Silvia Bertagna in third.
And that was enough to crown her champion by just one point from Switzerland’s Sarah Hoefflin, with Eileen Gu taking third.
In the men’s, Mac Forehand claimed the overall slopestyle title, despite finishing 12th in Silvaplana.
Andri Ragettli took his first slopestyle victory since January 2018, with Colby Stevenson second and Fabian Boesch third.
Forehand finished 34 points clear of Max Moffatt to take the title.