Perry Hall's rush carried over to the final quarter, and the Gators began it with an 8-2 spurt to make it 32-27 with 3:43 remaining.
The Gators led 36-30 with 1:43 to go before Katie Railey's three-pointer trimmed the margin to 36-33 about a minute later.
Perry Hall, however, sealed the win as Dietrich sank three free throws in the final 30 seconds.
"We had too many turnovers and couldn't hit anything down the stretch," said Notre Dame Prep coach Katie Marks, whose team committed 24 turnovers and shot 27 percent (13-for-47) from the field. "We always expect them to come back, but we expect to rally past the run.
"We talk constantly about runs and that our run has to be the last one," she added. "It wasn't today."
Camille Becker and Sabrina Hall had four points each for winners.