The Hilltoppers (31-30) also beat the Lady Hornets in a first-round game Tuesday before losing to Kennesaw State later that afternoon.
Next up for WKU is an elimination game at 9 a.m. Thursday against regional host Georgia State.
The Toppers led 2-1 after two innings Wednesday before busting the game open with four runs in the third inning and six in the sixth.
Jordan Mauch drove in three runs for WKU, while Haylee Towers, Brittany Vaughn, Rebekah Engelhardt and Adarian Gray tallied two RBIs apiece. Towers, Vaughn, Engelhardt and Gray scored two runs each.
Towers pitched the first five innings, allowing one run on six hits and a walk while striking out two.