Shiffrin clocked one minute 13.62 seconds, 0.12 seconds ahead of Elena Curtoni from Italy. France's Romane Miradoli took third place, 0.40 seconds behind Shiffrin.
"That was the best run I could possibly have," a delighted Shiffrin said. "I don't know if it felt perfect, but what I've learned over the years in super-G is that you can't really do it perfect."
She now has three wins in nine starts this season and leads the World Cup standings by 105 points over Italy's Sofia Goggia.
The World Cup takes a break over Christmas before resuming with two giant slaloms and one slalom in Semmering on December 27-29.