The Trojans led 35-31 early in the second half before using a 12-2 spurt to take a 14-point advantage. The Longhorns rallied behind Kathleen Nash, who hit consecutive 3-pointers to make it 55-51 USC with 3 minutes left.
Hughes and LaPlante scored the next six points to put the game away.
Nash scored 17 points and Brittainey Raven added 15 for Texas (3-2). Ashleigh Fontenette, who had 20 points in a win over Mississippi State on Thursday, was 1 for 11 with three points.