Fay scored the first and last tries of the match, as well as producing a brilliant covering tackle when the game was tied at 12-12, just as the Indigenous looked set to score a length of the field try.
Co-captain Shannon Mato and fullback Gayle Broughton, on her way to the Trish Hina Medal as Player of the Match, also starred for Keith Hanley's side, as they won the annual clash for the third time.
The Māori raced out of the gates to score twice in the first quarter, while holding the Indigenous to a penalty goal, but at half-time the gap had been reduced to 8-6.