Canada put up a valiant fight but could not prevent another Korean one-two at the Audi ISU World Cup Short Track.
This is Shum’s second gold this World Cup season.
"It's good. The reason I'm happy is that through this race I can be sure of my ability. Now I feel very confident," she said.
Leader for much of the race, Shim was not affected by the drama behind her.
"I wasn't exactly worried. I was focused on the race."
Choi could not get through St-Gelais and Maltais to reach the race leader Shim, but St-Gelais was evasive about the strategy.
“Sometimes having a strategy can do the opposite, so instead of playing for us, it's playing against us. We know if a teammate is in front of me, I'm not trying to do something bad on her and vice versa,” she said.
“We stayed focused on the race. With four laps to go, so many things can happen in Short Track, but I was confident I, or both of us, could get on the podium.”
This is the third Korean one-two this world cup series, after the men did it twice in Budapest.