The Senecas defeated Cooperstown 60-49 in the Class C state quarterfinals on Sunday at the Floyd L. Maines Memorial Arena in Binghamton.
Watkins Glen led 27-19 at the half.
Taylor Kelly scored 20 points for the Senecas and Hannah Morse added 17 points for Watkins Glen.
Watkins Glen (20-4) will head back to the state semifinals for the first time since they won a Class C state title in 2017.
The Senecas will play Millbrook in the Class C state semifinals on Friday at 1:30 p.m. at Hudson Valley Community College.