The Terps' bats fell quiet in game one but roared to life in game two for a mercy-rule victory.
The Terps have not clinched a series at the Maryland Softball Complex in nearly three years.
Nelson drove in three runs to lead the way for the Wildcats.
Haley Ellefson knocked in the winning run to give the Wildcats their second loss of the season in game one.
The Terps lost their third straight game by at least eight runs.
It will be the first time coach Mark Montgomery will play a game in the state of Maryland.
The Buckeyes scored six runs in the fourth inning.
The Terps exploded late in the first game for a six-run victory, while the Buckeyes won on mercy rule in the second contest.
The Terps managed just three hits against the Buckeyes' Allison Smith.
Six of the Terps' first 12 contests have gone beyond seven innings.