Auburn led 31-29 at halftime and quickly built a seven-point lead on a lay-up and three-pointer from Alli Smalley to open the second half, but the Tigers had a difficult time holding GW off the offensive glass from then on.
The Colonials had 12 offensive rebounds in the second half after being out-rebounded 17-8 in the first 20 minutes. Adair had a double-double in the final 20 minutes alone.
George Washington, which improved to 26-6, will play the winner of California and San Diego. Auburn, which made a stride in the right direction with its first tournament appearance under Coach Nell Fortner, finished the season 20-12.
Prior to the loss to George Washington, Auburn had won its previous 15 first round NCAA Tournament games.
George Washington led for much of the first half, but the Tigers went on a 9-2 run late to claim a halftime lead. Auburn fell behind 8-3 early on a pair of threes by GW's Antelia Parrish and a pair of free throws by Adair.
Trevesha Jackson cut the deficit to three, and both teams went cold for the next three minutes until Parrish buried another from long range to put the Colonials up 11-5.
Six points was the largest first-half lead for the sixth-seed Colonials of the Atlantic-10 conference and 11th-seed Auburn chipped away slowly during the first half. A jumper by Jackson tied the game at 22 apiece and Cassie Moore's lay-in gave Auburn its first lead since 3-0. Two made free throws by Moore with 11 seconds remaining in the half capped off a 9-2 Auburn run to give the Tigers a 31-26 advantage. However, in all too familiar fashion, the Colonials hit a late three to make the halftime score 31-29.
Sherell Hobbs drives in Saturday's game.
Bonner, after leading the Tigers with 12 in the first half, picked up where she left off with a baseline jumper to extend Auburn's lead back to four. After a bucket for the Colonials, Smalley's five points put the Tigers up by seven before the charge on the glass from George Washington.
Lawrence nailed a three-pointer and out-raced the Auburn defense down the court for another easy bucket to pull within two. Atlantic 10 conference player of the year Whitney Allen tied it at 46-46 and from then on it was all Adair. Even her twin sister, Jazmine, got in the action with a hoop, harm and free throw as the Colonials pulled away for the victory.
Bonner led the Tigers with 16 points and six rebounds. Sherell Hobbs added 10 points and eight rebounds and Jackson had 10 points and five boards.
"I thought we fought really hard today, we just couldn't really knock down some shots in the second half," Fortner said. "I thought GW was a fine basketball team and they just overpowered us in the second half.
Senior point guard Tamela McCorvey was able to play just four minutes due to a groin injury that has plagued her the past month.
"I was proud of how hard we played, but you have to knock down shots and we just hit a period of time where shots weren't dropping for us and they made a pretty good run at us. Hopefully, this experience will carry over for us next year."
The Tigers hit just 28.1 percent of their shots in the second half to finish at 34.5 percent for the game compared to GW's 42.1 percent.
Auburn hit 3-14 threes and 13-16 free throws. GW made 6-17 threes and 12-16 foul shots.
"They are a very physical defensive team, they're very tough and they had a big post presence inside and I think we were pretty much outmatched inside," Fortner said. "I thought we were trying to do some things to try to affect their post players and we did at times, but in the end I think it wore us out.
"They do a great job in that matchup zone denying and playing it like a man. I think they're a very good basketball team."