At the last intermediate time, the Swede was 0.44 ahead of leader Petra Vlhova, but a rough miss at the end caused her to lose second place.
Shiffrin couldn't do anything even with a flawless run.
Shiffrin won by a crushing 0.76.
Although Shiffrin went out last and had to ride in the worst conditions, she was fourth in the second run.
Shiffrin is now just one win behind Lindsey Vonn's women's record of 82 World Cup wins.
Ingemar Stenmark's total alpine record is 86.
Swenn Larsson was radiantly happy when she stepped onto the podium after her tenth podium.
The other two Swedes ran out in the second run
Wendy Holdener was sixth after the first run and came down with a 0.98 lead after a very good run in the difficult conditions where she mastered the bumpy course with potholes, embankments and ruts to finish fourth.
Petra Vlhova broke that time by 0.62 after a stable run.
The Slovakian was third after the first run.
Hanna Aronsson Elfman was seventh after the first race but crashed out in the second.
So did Moa Boström Mussener, who was 27th after the first run.
Seven riders drove out.