It is the fourth CIS title for the Martlets, who were dethroned as Quebec conference champions in each of the last two seasons by the Carabins, who captured the CIS banner last year.
"It's very overwhelming but this is what we wanted so all we're very happy and I'm beyond words," said Fouracres, a defenceman from Calgary. "All I wanted was for the puck to go in that net. I know I've scored on her in that spot before so I was going with it and am glad it worked out."
Tournament MVP Gabrielle Davidson struck twice and assisted on the winner for the Martlets, who had a 33-24 edge in shots. The sophomore from Pointe Claire, Que., finished the CIS tournament as the top scorer, with six goals and nine points in three games.
Davidson gave McGill 1-0 and 2-1 leads, sandwiched around Ariane Barker's first of two for the Carabins.
Michelle Daigneault, a senior rearguard from Hay River, N.W.T., gave McGill what appeared to be an insurmountable 3-1 lead at 10:17 of the third period. But the Carabins scratched their way back to tie the game at 3-3 on goals by Janique Duval of Val d'Or, Que., at 11:00 and Barker of Napierville, Que., at 16:47 to force overtime.
Carabins defenceman Sophie Brault was called for holding with 20 seconds remaining in the 10-minute sudden-death period. McGill capitalized seconds after returning to the ice for a second extra period.
"I'm just so happy for those girls, they worked so hard," said McGill head coach Peter Smith. "We've got four graduating players and what a way to go. I'm just thrilled for them."