Sessions was 5-of-9 shooting and 8 of 9 at the foul line for the Gamecocks (19-3, 7-2). Tiffany Mitchell and Aleighsa Welch each added 10 points.
Reigning SEC Player of the Week Ieasia Walker pitched in eight points on just 2-of-7 shooting for South Carolina, though she did dish out five assists and record four steals.
Auburn's Hasina Muhammad entered having scored in double figures in 23 straight games -- the eighth-longest streak in the country -- but managed just seven points Sunday.
Tyrese Tanner and Tra'Cee Tanner each had 10 points for the Tigers (13-9, 2-7), who have lost six straight and seven of eight.
South Carolina's defense held Auburn to just 39.3 percent shooting (22 of 56), including 2-of-8 3-point shooting.