The Cowgirls (2-1) led 21-17 after the first quarter, but the Pioneers grabbed a 40-37 lead at the half and continued to extend their lead in the second half.
Tereza Vitulova led UW with 13 points and Quinn Weidemann added 12, but they were the only two Cowgirls to finish in double figures. McKinley Bradshaw (Lyman) finished with eight points while Alba Sanchez Ramos pitched in seven points and a team-high nine rebounds.
The Cowgirls return to action Sunday when they host Colorado at the Arena-Auditorium. Tip-off is scheduled for 1 p.m.