The Sooners (22-8) face rival Texas (28-3) on Saturday for the championship and an NCAA tournament berth.
Oklahoma roared to a 49-35 halftime lead after hitting 8-of-11 3-pointers, and regular-season co-champion Kansas State (24-5) never recovered. The Sooners made 53 percent (10-of-19) of their 3-point shots.
The Wildcats pulled within 10 points twice in the second half, but never really threatened.
Kansas State did have one consolation, with two-time Big 12 player of the year Nicole Ohlde setting the league record for career scoring. She had 18 points, giving her 2,193 for her career.
Ohlde passed the 2,187 points Phylesha Whaley scored for Oklahoma from 1997 -2000, hitting a short turnaround jumper that cut the deficit to 69-57 with 2:30 remaining.
Laurie Koehn added 18 points for Kansas State, but was 6-of-20 from the field. Kendra Wecker added 13 points, but she was 6-of-17 as the Wildcats shot just 37 percent.
Dionnah Jackson added 15 points for Oklahoma, and Erin Higgins had nine, all on 3-pointers. Villarroel was 3-of-5 on 3-pointers, and Rush was 2-for-3.
After Kansas State tied the score at 12, Oklahoma went on 24-8 surge. Villarroel had seven points, three assists and two steals in the run.
Villarroel added 12 rebounds for Oklahoma, which won the battle of the boards 43-28.
Kansas State beat Oklahoma 74-65 in January. That was Oklahoma's fourth straight loss, but the Sooners have won nine of 11 games since. Villarroel did not score in just two minutes of action in that game.
It will be Oklahoma's third appearance in the tournament final. The Sooners beat Baylor in 2002 and lost to Iowa State in 2001.
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