The Tigers join Campbellsville (Ky.), Cumberland (Tenn.) and Shawnee State (Ohio) as MSC members still alive in the now 16-team bracket.
Georgetown scored 21 of its 38 second half points from the free throw line, including its last 16 points in the final three minutes of play.
Lyon opened the game with a quick lead and saw six lead changes during the first eight minutes of play before the Scots took the lead on a 3 by Phagen Altom, who led her team with 17 points. Lyon controlled the lead the rest of the first half, going up by six, 29-23, before Andrea Howard and Devon Golden hit back-to-back buckets to close the half. Golden's was a 3 with six seconds left to cut the score to one, 29-28, entering halftime.
Georgetown's momentum carried into the second half, as Howard connected on an and-one play to give her team the lead. Lyon tied it twice but a pair of Howard free throws, with 17:29 left, gave Georgetown the lead for good.
Howard, a Frankfort native used to playing in the Frankfort Convention Center in both high school and in college, led all players with 24 players.
The second half hit a lull, as both teams went scoreless for five minutes before Devanny King ended the drought and Howard followed with a 3 to give the Tigers' their first double-digit lead, 50-38, with 7:14 remaining. Lyon managed to cut it to six points with four minutes left, but Georgetown was too steady from the free throw line.
Lyon finishes the season with a 28-5 record.
Georgetown, a four-seed, will meet No. 1 seed Lubbock Christian (Texas) in the second round Friday at 8 p.m. EDT.