The slalom world champion beat in-form Swede Maria Pietilae-Holmner and France's Nastasja Noens to emerge as the US women's team's best chance of a gold medal in Russia next month.
Asked whether she would be the only female American contender at the Olympics, Shiffrin said: "I'm sure the speed team will return to form in January but at the same time, we all race for ourselves and for me this is an important victory after two unexpected defeats."
Shiffrin was a lowly 12th in Courchevel before Christmas and second behind Marlies Schild in Lienz after clinching the season's inaugural World Cup slalom in Levi, Finland, in November.
US Ski Team coaches Patrick Riml and Alex Hoedelmoser gave news of Vonn's rehabilitation work in the finish area of the Bormio stadium and hinted that the defending Olympic downhill champion might not be seen back in action before the Olympics.
"Her knee is very swollen and it's impossible for her to consider skiing for now," Hoedlmoser told journalists.
Vonn tore knee ligaments at the world championships in Schladming in February and revived the injury in training in Copper Mountain in November, a new incident which was probably more serious than originally thought.
She was forced out of the last downhill she entered in Val d'Isere last month after her knee failed her.
"To race without a ligament is extremely risky and can have serious consequences. If she was a young athlete, we would have stopped her already," Riml said.
Vonn was planning a further test in one of her favourite resorts in Cortina d'Ampezzo on January 18-19 but her return now looks doubtful and the coaches may consider entering her for the Sochi downhill without any other prior race.
"It totally depends on how she recovers, how the knee feels, if she gets the strength back, the stability in the knee," said Hoedlmoser. "But the Sochi course is not very difficult and would suit her ideally in normal circumstances."
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