Napavine got a game-high 21 points from Demi Sahlinger and outscored DeSales 21-11 in the second half to overcome a five-point halftime deficit and defeat the Irish.
The Tigers held DeSales to 4-of-26 shooting in the second half and made 8-of-12 free-throw attempts in the third and fourth quarters.
Abby Crowley scored 10 points for DeSales and was the only Irish player to score in double figures. She also led the team with two assists.
With the win, Napavine placed fourth in the WIAA 2B Girls State Basketball tournament.