The Longhorns had trouble breaking free from the Flames and led by just 44-37 near the 5-minute mark of the third quarter. A 15-2 run led by Madison Booker with six points and Taylor Jones with five points put Texas in control 58-39 after three.
The Flames outscored Texas 9-5 through the first six minutes of the fourth quarter but never got closer than 15 points.
Jones had 13 points and seven rebounds off the bench for Texas (2-0) and Booker scored 11.
Led by 11 points from freshman Ella Wigal and 10 from Elisabeth Aegisdottir, another freshman, Liberty's reserves outscored the starters 37-20.
Liberty committed 15 turnovers in the first half but kept it close by shooting 52% from the field compared to 33% for the Longhorns. Harmon led Texas with 10 points on 4-of-7 shooting and added four assists.
The Flames finished with 35 turnovers, and Texas was credited with 18 steals. The Longhorns had 10 turnovers.
Liberty has lost 39 in a row against Top 25 opponents.
Texas hosts UT Arlington on Tuesday.
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