Barraco made seven saves for the Nittany Lions as the Terps dropped their second straight game.
The senior has four points in three games.
Donnelly scored and added an assist across Maryland's two games last weekend.
Wildcats forward Bente Baekers slotted past Noelle Frost late in the fourth quarter to secure the victory.
Donnelly has taken more shots than anyone else in the Big Ten through two games.
The Terps failed to find the back of the net on nine penalty corner attempts against Northwestern.
The Wildcats scored two goals in the third quarter to get past the Terps.
Fueled by goals from Kyler Greenwalt and Sam Zywna, the Terps rolled past the Spartans.
“One of our biggest [strengths] is being comfortable with the unknown," defender Riley Donnelly said.