The Wahine (20-7) also gave their coach, Vince Goo, his 200th career win.
Rice had trailed most of the second half but rallied behind six 3-pointers, the last by Marla Brumfield with 3:48 to go to put the Owls ahead, 51-50.
The victory lifts Hawaii into Friday's 10:30 a.m. semifinal against the winner of today's game between San Diego State and New Mexico. The Wahine split their two regular-season meetings with the Aztecs (20-6) and the Lobos (18-9).
Should Hawaii win Friday, it would put the Wahine into Saturday's 12:30 p.m. championship.
Senior center Kendis Leeburg scored 21 points, including 10 in the first half.
Howard, the WAC Pacific Division Freshman of the Year, finished with 13 points.
The Wahine threatened to break open the game midway through the second half, taking a 44-39 lead on two consecutive baskets by Leeburg. But the Owls continued their torrid 3-point shooting (5 treys in a row in the second half), with Brumfield's 3-pointer knotting it at 44-44 with 8:22 to go.
Women
Today's games
Hawaii vs. Rice, 10:30 a.m.
San Diego St. vs. New Mexico