Montague led for most of the game until Fremont junior Hali Garcia tied the score with a buzzer-beating 3-pointer that sent the game to overtime.
Garcia went on to score seven of her 17 points in overtime to push the Packers to victory.
Bre Harris led Fremont with 18 points and 11 steals. Sydney Stine had 17 points, six rebounds and four assists for Montague while McKenna Lohman added 16 points and 10 rebounds.
Fremont improved to 6-2 on the season.