Haeger allowed five hits and struck out five. She reached base on all four of her plate appearances, earning most outstanding player honors.
Florida became just the third program to repeat as Women's College World Series champion, and the first since Arizona in 2006-07.
The players threw their gloves up in the air, and Haeger jumped up and down excitedly in the pitcher's circle before she was rushed and the team formed a pile.
The Gators (60-7) scored all their runs in the first two innings. Justine McLean had two hits and Taylor Schwarz knocked in two runs for Florida.
Michigan (60-8) was going for its first title since 2005. Haylie Wagner, who shut out Florida on Tuesday to keep the Wolverines alive, got the loss. Megan Betsa gave up only one hit and didn't yield a run in four innings of relief.