The Terps are introducing renewed depth behind Okonkwo, who missed 2020 due to health issues.
The Terps beat then-No. 18 Charlotte and UMBC to climb the rankings.
The trio secured a bronze medal for Team USA at the Junior Pan American Championships.
The freshman forward scored in his first game as a Terp and impressed players and coaches throughout opening weekend.
"We saw a lot of fight when we went down," coach Ray Leone said.
"Everyone’s going to know who Milan is by the time she finishes here," coach Adam Hughes said.
The Terps scored three first-half goals and held off a late charge from the Retrievers to remain undefeated.
The Terps scored in the opening minute of the game, but struggled to keep up with the Midshipmen's attack.
A diving save from Bibi Donraadt kept the Terps alive.