Shenandoah (12-8) got the 2-1 ODAC semi-final round win as freshman Taylor Hayes converted a Morgan Payne penalty corner 4:30 into the sudden-victory period to eliminate Lynchburg (11-7) from tournament contention.
The win is the first-ever for SU over LC in 15 lifetime meetings.
"This is the greatest win ever!" Shenandoah head coach Ashley Smeltzer-Kraft said.
"The women played a great game tonight and followed the game plan perfectly.
"I am so proud of them."
The victors held that lead until Lynchburg brought the game back to level 7:03 into the second half as Kayla Copeman set up Nicole Simpao right in front.
In the OT, LC had the first shot (by Simpao) before Elizabeth Pardo set up the game-winning goal by taking possession in the Shenandoah defensive end and advancing all the way into the striking circle.
A foul was called as SU attempted to get off a shot, which led to the game-winning penalty corner.
Morgan Payne inserted to Hayes at the top of the circle, and Hayes ripped her shot just inside the left post for the game-winner.
"It was all a blur," Hayes said of her game-winning goal. "I remember Morgan passing me the ball and then hearing the ball hit the board.
"That (the shot) is what we have been working for all season long."
Shenandoah will play third-seeded Washington and Lee Saturday at 6:30 on Lynchburg College's Shellenberger Field for the championship. The winner of that game earns the league's automatic berth into the NCAA Tournament.