Fifield scored the game-winner with 24 seconds left off an assist from Sam Stevenson. JMU is the fourth Top-20 opponent Richmond has faced in its rugged non-conference schedule.
The Spiders won their third in a row as they improved to 3-3 on the season.
After a 2-1 JMU lead early, Richmond powered seven-straight goals through to take a 8-2 lead with seven minutes remaining in the first frame. In that scoring onslaught, Fifield scored two, Sam Stevenson two, and three other Spiders recorded a tally each.
JMU would respond mightily with five consecutive scores to slash the Spider advantage to 8-7 heading into the break.
Richmond opened the second half with two straight scores, by the sticks of Kara Moschetti and Flowers. The Dukes quickly responded with two scores of their own to keep the score at a 10-9 Richmond advantage.
Richmond tried to distance itself from Madison with two more scores, but it countered with three-straight goals to knot the game at 12-all with 33 seconds left. Fifield then scored the game-winner to seal the win for the Spiders.
Besides Flowers and Fifield's hat tricks, Stevenson added two goals, as did Moschetti. Three other Spiders recorded a tally each.
Stevenson ended her day with a team-high seven points, off two goals and a team-high four assists. Flowers followed with three dishes, as Richmond notched 10 for the game.
Richmond recorded 16 ground balls and Victoria Roebuck recorded six saves in the net.
The Spiders travel to No. 3 Maryland Tuesday for a 7:00 p.m. draw.