Katie Pritchard had 22 points - including 18 in the second half - to lead the Lady Panthers, who fell to 8-8 overall and 2-6 in the GLVC. Maryville improved to 9-7 and 5-3.
Duethman scored 13 of Maryville's first 20 points to stake the Saints to an early double-digit lead, but Drury fought back to trail 25-21 at the half.
Drury cut the deficit to two on a couple of occasions in the second half - the last time at 42-40 with 10:40 to go after a Pritchard 3-pointer - but could never get completely over the hump. The Lady Panthers trailed by five (48-43) with 6:54 left, but Maryville outscored DU 11-4 over the next five minutes to pull away.
Drury was hampered by 24 turnovers in the contest, 14 coming in the first half.
Maryville committed 21 miscues, but held the Lady Panthers to 34 percent shooting (16 of 47) while hitting 42 percent (22 of 52) - including 50 percent in the second half (12 of 24) - to get the triumph.
Bethanie Funderburk added 11 points for the Lady Panthers, who also got a team-high nine rebounds from Kylie Williamson, matching her career high. Funderburk and Abby Bracker added six boards each for DU, which lost the battle of the boards 33-32.
Pritchard hit four more 3-pointers (in nine tries) to move her school-record total to 237, while Funderburk moved into eighth place
Drury will stay in St. Louis to play Missouri-St. Louis in a 1 p.m. GLVC tipoff on Saturday.