Millea scored seven minutes into play off a crossing pass from Hall. Hall then scored on a breakaway 11 seconds before halftime to make it 2-0.
After West Canada Valley scored seconds into the second half, Hall scored again on a breakaway to give Cooperstown a 3-1 lead.
Jordian Siver also scored for Cooperstown, which received 18 saves from Katie Kleban.
“She had some great saves,” Cooperstown coach Jennifer Pindar said of Kleban.
Cooperstown (3-1, 2-1) will host Frankfort-Schuyler on Thursday.
Margaretville 2, Jefferson 2
Emily Wenner’s goal with 10:45 left in regulation lifted visiting Jefferson to a Delaware League tie.
Wenner scored on an 18-yard shot from the left side.
Christina Westerfield had a goal and an assist as Margaretville took a 2-1 lead into halftime. She set up Cecilia Galatioto’s goal, then scored on a header off a corner kick by Cora Bruno that gave the Blue Devils a 2-0 lead 22:48 before halftime.
Jane Clayton scored with 1:37 left in the first half for Jefferson.
Margaretville (0-2-1) will play Coleman Catholic at 7:30 p.m. Thursday in a first-round game of the Cohen Tournament at Margaretville.