Simmons scored 18 of her 29 points in the second half against the Tigers, who built a 12-point lead and then faded in a 75-66 loss to No. 9 Tennessee on Thursday night.
"It was definitely frustrating," Auburn's Blanche Alverson said. "I felt at one point we couldn't do anything right and we were trying too hard to turn it back around.
"The coaches in one of the timeouts said we have to play to win, not play to not lose."
Simmons followed a three-point play with back-to-back 3-pointers in a 15-2 surge that turned the game against Auburn (13-5, 2-3), which got only five points from its reserves. The Lady Vols and coach Holly Warlick sensed the turning point.
"When I made that (three-point play) it got everybody off the bench and even Holly was jumping on the sideline," Simmons said.
The Lady Vols (14-3, 5-0 Southeastern Conference) used a 40-15 run to take control of a game they'd trailed most of the way en route to their seventh consecutive win.
Simmons, who had 27 points in an overtime win over Florida, made 10 of 14 shots—including 4 of 6 from 3-point range.
Taber Spani had 12 points for the Lady Vols and Ariel Massengale added 11. Simmons also had six turnovers against a pressing defense that Auburn couldn't maintain.
"She's such a competitor and you could tell she was getting frustrated with herself and we were telling her, 'Stay in it. Stay in it,'" Spani said. "She poured it on in the second half."
Hasina Muhammad and Alverson scored 15 points apiece to lead five Auburn players in double figures. Najat Ouardad had 11 points, eight assists and four steals, while Tyrese Tanner and Peyton Davis each had 10 points.
The Tigers led by as many as 12 five minutes into the second half.
"I thought our girls felt really confident and they played very, very hard," Auburn coach Terri Williams-Flournoy said, adding that lack of depth affected her starters down the stretch.
Tennessee shot 54 percent (15 of 28) after erasing most of an 11-point deficit to trail 32-27 at halftime. The Lady Vols were also 8 of 16 from 3-point range and made all four long-range attempts in the second half.
"I think tonight we found a way to win," Warlick said. "It wasn't pretty for us. I think Auburn just played a heck of a game. At halftime we went in and made a couple of adjustments, but we just challenged our players. We were flat and I think Auburn had a lot to do with the way we were playing. They were aggressive and we weren't."
Simmons had four steals and was perfect on five free throw attempts.
Bashaara Graves and Isabelle Harrison both had 11 rebounds for the Lady Vols, who have won five straight over Auburn.
The Tigers, meanwhile, have dropped two straight to ranked teams, including a 22-point loss at No. 20 Texas A&M.
"The thing about Tennessee is they score in bunches," Williams-Flournoy said. "When you make a turnover, nine times out of 10 they're going to score off your mistake."
The Lady Vols pushed the lead to 65-59 when Spani hit a basket, was fouled and made the free throw with 4:12 remaining. Simmons hit two free throws during that stretch after Auburn was hit with a technical foul for a substitution miscue when Ouardat entered the game that left six players on the court. The Tigers never rebounded from there.
"I definitely think it was a mishandling of that situation by the officials," Williams-Flournoy said.