The Blue Devils have won their tournament 13 of its 16 years.
The Blue Devils (4-1) struggled to get the ball inside midway through the second half. Auburn (4-2) was outrebounding Duke and post players Iciss Tillis and Mistie Bass were saddled with four fouls.
Auburn recovered from a 39-31 halftime deficit, as seven points from Le'Coe Willingham sparked a 10-1 run.
"Their zone was really destructive to our game," Duke coach Gail Goestenkors said. "They were killing us with our post players in foul trouble."
Tanesheia Thompson's basket with 7:53 to play gave the Tigers a 55-53 lead. Goestenkors then pulled the 6-foot-5 Tillis off the bench and ordered Duke into a 1-3-1 zone, with Beard getting the assignment of disrupting Auburn's passing.
"We needed Iciss back in there for some size, and that was the decisive moment of the game," Goestenkors said. "That's when we picked up our defensive intensity."
Duke scored 11 unanswered points, and the Tigers missed their last 12 shots from the floor and turned the ball over on five possessions.
Duke limited Auburn to a pair of free throws in the final 7:53.
Monique Currie and Tillis combined for nine points in the decisive run, and both finished with double-doubles. Currie had 14 points and 10 rebounds, and Tillis added 11 points and 11 rebounds.
"You spend a lot of time worrying about Alana, and then here come Monique and Iciss," Auburn coach Joe Ciampi said. "That was backbreaking for us. They just have so many weapons."
Willingham led Auburn with 19 points, but she was held without a point in the final 12:52.
"They went into that zone and made it difficult for my guards to get me the ball," Willingham said.
Willingham had nine rebounds as Auburn became the first team this season to outrebound Duke, finishing with a 34-30 edge. The Tigers also held the Blue Devils to a season low in points and shooting percentage (42 percent), one night after Duke's best-ever shooting night (68 percent) against Stephen F. Austin.
"That was very disappointing," Goestenkors said. "Rebounding has been a point of emphasis for this team. I guess the best thing we can take away from this is that we played a very, very good opponent and found a way to get away with a win."