Cutler, who had already won the 16/17-year-old girls’ 100m and 200m backstroke crowns in Sheffield, triumphed in the 50m event of the fifth day of the competition.
The teenager clocked 30.16 to win by more than two tenths of a second.
Jacob Newcombe was also on the podium for Mount Kelly on Saturday. He won silver in the 14-year-old boys’ 100m backstroke in a personal best time of 1:03.39.
There was a bronze medal for Plymouth Leander swimmer Lucy Burchell in the 15-year-old girls’ 50m backstroke.