Plum's free throws allowed the Huskies (15-10, 8-6 Pac 12) to survive a 3 from Chiera Dunbar with 2 seconds left for Utah (10-15, 3-11).
Jazmine Davis added 17 points for Washington, which made 19 of 24 free throws while the Utes were 3 of 5. Federal Way product Talia Walton added 10 points for the Huskies.
Michelle Plouffe scored 31 points for Utah, tying her career high, and grabbed 14 rebounds to give her 1,106 for her career, tying the school record.
Washington, which led 31-29 at the half, took the lead for good when Chantel Osahor's 3-pointer broke a 60-60 tie with 3:33 left. Plouffe's layup with 36 seconds to go made it 64-63. Plum made two free throws at 32 seconds and after Plouffe missed a 3, Plum rebounded and made 1 of 2 at 10 seconds.