At East Sullivan, Ellsworth took a 12-point lead at the end of the third quarter and then held off the Tigers for the victory.
Catlin Bean paced the winners with 14 points while Emily Berry and Morgan Card each added 11 points.
Savana Turner and Taylor Davis each scored 14 points to lead the Tigers and Jordan Merchant added eight.
Ellsworth 11 34 45 53
Sumner 2 14 33 52