Cameron Graupman hit a three pointer for Hilton to tie the game at 51 with 12 seconds left in regulation. Both teams were scoreless during the first three minutes-plus of overtime.
Lauren D'Hont led Mendon with 18 points and seven rebounds for the Vikings. Valentine had ten points and five boards.
Amy Hasenauer paced Hilton with 18 points.
Mendon is 8-0. Hilton falls to 5-3.
Vikings miss chance in final seconds
Monarchs scare New York's top team, but fall in state semis