Italian Michela Moioli took gold and bronze went to Eva Samkova of Czech Republic at the end of a terrific clash at the Phoenix Snow Park.
Pereira de Sousa Mabileau finished ahead of reigning Olympic champion Eva Samkova, five-time world champion Lindsey Jacobellis and compatriot Chloe Trespeuch.
“My objective was to make the final. After that, I had nothing to lose,” said a confident Pereira de Sousa Mabileau.
“Maybe it is being young - although it is now a year and half that I have been on the world cup circuit - but I’ve never been afraid.
"In fact, I am never like that. I never get afraid - I just go for it.
“It is a bit crazy to find myself in the final with girls much older, who have much more experience than me,” she added.
“I was watching these girls on the television when I was four, and at Sochi.
“A silver medal? It is unbelievable, I am so happy.”