Oklahoma (3-0) will play Vanderbilt, an 81-39 winner over Lipscomb, in Saturday's championship.
Sharane Campbell also added 13 points for the Sooners.
Liberty (2-3) hadn't played a ranked team since Dec. 28, 2010. The Flames hurt themselves with too many turnovers as Oklahoma forced 19 of 37 turnovers in the first-half and finished with 38 points off those mistakes. The defending Big South champs did outrebound Oklahoma 47-34.
Terika Lunsford led Liberty with nine points and had 10 rebounds. Avery Warley and Catherine Kearney each grabbed 10 boards.
Oklahoma opened by scoring the first six points and led 10-1 before Liberty scored from the floor on a jumper by Danika Dale with 17:12 left. The Sooners, perhaps still getting used to quirky Memorial Gym, went nearly six minutes without a bucket.
That allowed the Flames to pull within 12-10 on a 3-pointer by Lunsford with 12:16 to go. That was as close as they'd get.
Hook answered with consecutive layups off the fast break, and her free throw to finish off a three-point play on the second put the Sooners back up 17-10 with 10:50 left. Oklahoma led 37-22 at halftime.
The Sooners just pushed the lead in the second half as they hit four of their first eight shots. Liberty hit just one of its first nine attempts as Oklahoma went up by as much as 38 when Harden scored on a layup off another turnover with 4:40 left for a 71-33 lead.