The score was 1-1 at half time courtesy of a Steph Nicolson goal from a slick penalty corner, as Bethlehem College slowly started to stamp their mark on proceedings.
Too many touches coming out of defence hurt Tauranga Girls', who routinely gave up possession in their own end to place goalkeeper Sofia Ellerington under increasing pressure.
Robinson ran and ran to give her younger teammates a chance, but no amount of pace or competitive nature could keep her side in the contest considering they had defeated Hamilton Girls' earlier in the day.
Bethlehem added goals to Kate Porter and Caitlin Procter after half time to claim the title, with coach Lincoln Churchill saying the win provides a boost for his players ahead of the school's first appearance in the top 16 division at nationals in early-September.
"It was always going to be tough and we probably didn't have out best night tonight, but we did enough and the girls fought really hard," said Churchill.
"Tauranga Girls' is a good side so it was really pleasing."
Bethlehem failed to match Tauranga Boys' in the second final, going down 3-0 in a more one-sided contest.
Hamish McGeorge scored a double and was a menace in both general play and from penalty corners, after Thomas Reid used some nice misdirection to open the scoring late in the first half from a well-executed penalty corner.
Girls: Bethlehem College 3 (Steph Nicholson, Kate Porter, Caitlin Procter) Tauranga Girls' College 1 (Yasmine Woodhouse)
Boys: Tauranga Boys' College 3 (Hamish McGeorge 2, Thomas Reid) Bethlehem College 0.