Megan Smith's rink from Sudbury, Ont., clinched the victory when Nova Scotia skip Mary Fay clipped a guard with her last rock.
Fay sent the game to an extra end in the 10th when she drew her final stone in close to tie the score 5-5.
Smith, third Kira Brunton, second Mikaela Cheslock and lead Emma Johnson finished a perfect 8-0, while Fay's rink from Chester, N.S., that includes third Jennifer Smith, second Karlee Burgess and lead Janique LeBlanc wound up 6-1 to take silver.
Nova Scotia beat New Brunswick 7-6 in one of Friday's semifinals at Prince George Golf and Curling Club, while Ontario downed Saskatchewan 8-3 to advance.
Earlier Saturday, Saskatchewan beat New Brunswick 9-8 in an extra end to win bronze at the under-18 tournament.
Manitoba beat Ontario last week to win the men's title.