Paige Parker (25-5) gave up three hits and one run in 6 1/3 innings for the win. Paige Lowary got the save for the Sooners (58-9), who advanced to Sunday’s semifinals and are one win from reaching the championship series again.
Oklahoma’s Fale Aviu scored in the second inning when she avoided a tag at home. Kelsey Arnold reached on an error in the fifth and scored a single by Aviu. Romero’s blast pushed the lead to 3-0.
Ali Aguilar’s solo homer in the sixth put Washington on the scoreboard.
Washington pitcher Taran Alvelo (27-8) went six innings and gave up five hits and two earned runs for the Huskies (49-13).
Washington will play the winner of the Texas A&M-UCLA game Saturday in an elimination game.
Barnhill (26-3), USA Softball’s Player of the Year, helped put the Gators (57-8) within a victory Sunday of a spot in the championship series. On Thursday, Florida opened with an 8-0 victory over Texas A&M.
Chelsea Herndon doubled to score two in the top of the fourth. Janell Wheaton hit a solo homer in the top of the sixth and Kayli Kvistad hit a two-run homer in the seventh.
Aleshia Ocasio made perhaps the play of the game in the second inning when she ran into foul territory and caught a fly ball as she fell over a barrier.
LSU starter Carley Hoover (15-8) allowed two runs in five innings, and Allie Walljasper struggled in relief.
The Tigers (48-21) will play in an elimination game Saturday.