``I was really nervous because Columbia is an awesome team,'' said Suminski, who shot 10 for 16 from the field and 9 for 12 from the foul line. ``Once I made a few shots, I settled down.''
Mendham became the first public school to win the girls' Tournament of Champions since 1990, when JFK-Paterson beat St. John Vianney, 70-47.
Columbia, which trailed by 49-32 midway through the third quarter, made a valiant comeback, cutting the lead to 61-57 on a short jumper by Marcie Dickson with 54 seconds left.
Suminski then made one of two free throws. Columbia's Jazmine Wright, a 5-foot-10 Syracuse recruit, missed a three-pointer on the next possession. The Minutemen then sealed the win when Yale recruit Jamie Riposta sank two free throws, extending the lead to 64-57 with just 26 seconds left.
Mendham, which hasn't lost since falling to Haddonfield, 68-63, in last year's Group 2 state final, didn't have a starter taller than 5-8 and appeared to be in serious trouble when Columbia, pounding the ball inside at will, took a 13-6 lead midway through the first quarter.
Then Mendham employed a full-court press, and the Cougars had no answer.
Columbia, which beat Haddonfield, 61-49, to advance to the final, committed 14 first-half turnovers, including nine in the second quarter, when it was outscored by 19-6.
Molly Creamer, a 5-7 junior, scored nine points in the second quarter while Suminski added six in the period and 12 in the half.
With the score tied at 21-21, Mendham scored 13 unanswered points and 15 of the final 17 to take a 36-23 halftime lead.
Mendham shot 30 for 39 from the foul line, while Columbia was 6 for 7. Another key was turnovers, with Mendham committing 12 to Columbia's 21.
``This hasn't sunk in yet,'' Suminski said. ``I'm sure it will in time, but this is just unbelievable.''