Flinthills took a 8-2 lead after a quarter but could not maintain it through the half and Peabody took a 20-16 advantage at the break.
Peabody outscored Flinthills 16-7 in the third to take a commanding lead and followed through with the win in the fourth.
Tara Kemp led the Mustangs with 9 points and 5 rebounds. Kati Starks had 7 points and 7 rebounds.
Bayley Reiswig, Amanda Bell and Riley Batson each poured in 6 points for the Mustangs.