Yergin tallied for the 10th time this season in the 11th minute before finishing off a Dornesha Cottoms feed in the 20th.
The two goals were more than enough for SU to earn its sixth straight win over Eastern Mennonite (4-4-1, 1-1).
Shenandoah held the Royals to just two shots on the day and Hornets keeper Erin Septer had to make just one save in posting her 24th career shutout.
The Hornets ended up with a 22-2 advantage in shots and took all nine of the game's corners.
"I thought we had another solid defensive performance anchored by Michelle Krause."