Canada finished first in the round-robin portion of the tournament and advanced to a semifinal match Saturday, where they routed Switzerland 11-0.
Sabrina Harbec, Dominique Thibault and Melanie Gagnon scored the other markers for Canada.
Michaela Lanzl scored the lone goal for Germany.
Harbec opened the scoring for Canada early in the first period on a pass from Johnston, beating German goalie Viona Harrer.
Germany tied it at one at 13:06 on a two man advantage as Michaela Lanzl roofed a rebound under the crossbar over Shannon Szabados in the Canadian goal. It was the only goal of the tournament surrendered by the Canadian team.
Canada took control of the game early in the second when Thibault banged home a rebound at 4:04.
Johnston deflected a point shot to make it 3-0 before Riggs, off a pass from linemates Sarah Vaillancourt and Meghan Agosta, gave Canada a commanding 4-0 lead heading into the final period.
Riggs and Gagnon upped the score to 6-1 in the final frame to seal the victory.