Her bronze-medal finish behind Germany's Maria Hoefl-Riesch and Austria's Nicole Hosp only solidified her reputation as a big-race skier, too, coming as it did on the heels of a lackluster season on the World Cup tour.
"It's been a really tough season for me, and I've always just had that real belief that I can do it," she said.
Unlike Vonn, who has four overall World Cup titles and 59 victories, Mancuso never has especially shined outside of major events.
She has won just seven races in a 14-year career on the World Cup circuit nothing higher than seventh, this season but has nine career medals in the Olympics and world championships, including a silver in the super-combined at the 2010 Vancouver Games, where she won two silvers while Vonn won gold and bronze and all the world's attention.
That's probably because she grew up idolizing the Olympics far more than anything else.
"I get really energized," she said.
Mancuso entered the Games happily encouraging her reputation, and seemed totally validated at the finish of the slalom course, where she threw her arms in the air and shouted with joy, knowing she'd become only the third American to win medals at three Winter Olympics.
"See?" she gushed, moments later. "It works! It really works! Believing in yourself works. I got a medal today!"
Racing with her long brown hair flowing out from her helmet, the woman known as "Super Jules" who wears her own brand of lucky underwear scorched the downhill part of the race with a tremendous run from a late starting position the super-combined involves one run of downhill and one run of slalom to take the lead and give herself a chance at the podium.
"It was a very, very solid downhill run," coach Alex Hoedlmoser said. "From top to bottom."
But the slalom is hardly Mancuso's strength.
It's her weakest discipline, and she hadn't raced a slalom since a World Cup super-combined a year ago. Seven rivals sat within 1.27 seconds of her downhill time, among them Hosp, Hoefl-Riesch and Slovenia's Tina Maze all stronger slalom skiers.
"I knew I had to just give my best shot," she said. "It sure didn't feel good. I definitely had moments in my mind where I was thinking, 'This is not going to be good enough, but keep fighting.' I knew where to let it run on that last pitch and surprise! looked up and got a medal."
Mancuso acknowledged thinking her lead wasn't big enough to hold off the big slalom guns.
But after Hosp and then Hoefl-Riesch posted two of the four fastest slalom times on long and rugged course nine of 31 skiers did not finish Maze managed only a pedestrian one, giving Mancuso an opening.
She posted just the 13th-fastest slalom time, but it was enough to beat Maze by 0.1 seconds overall.
"I knew that it was possible," Mancuso said. "Definitely if the hill was easier, I would be thinking, 'I'm going for gold.' That was tough and I really just wanted to make it down with a clean run. I don't know if I could do any better. I could definitely risk more, but without having the slalom mileage, it's really tough to snap off turns and try to make up speed. It's more just survive and get to the finish."
Now, Mancuso has installed herself as a favorite for the downhill on Wednesday, as well as the super-G on Saturday and the giant slalom on Feb. 18. She has won Olympic or world championship medals in each one.
"It's cool," she said. "Now I know I can really be fast in the downhill, and I know how to be fast. It has a lot to do with aerodynamics. The same thing is, just keep on fighting till the finish and no matter what, be proud of the run, and I think I can have a great downhill, too." Mancuso joins the three-time club
Only three Americans have won medals at three Winter Olympics:
Julia Mancuso, Alpine skiing • 2006, 2010, 2014
Apolo Ohno, short-track • 2002, 2006, 2010
Bonnie Blair, speedskating • 1988, 1992, 1994
Ski racer Julia Mancuso is the only American woman to win medals of every color at the Olympics:
Gold • Giant slalom, 2006 Turin Games
Silver • Downhill, 2010 Vancouver Games
Silver • Super combined, 2010 Vancouver Games
Bronze • Super combined, 2014 Sochi Games