Wagga City produced a massive form reversal to end Griffith's unbeaten run.
Captain Kellie Allcorn's lone conversion was the difference between the two sides as the fourth-placed Boiled Lollies took a 17-15 win at Conolly Rugby Complex on Saturday.
After the Blacks took a 51-0 win when the two teams last met, coach Rob Cleland was thrilled with how his side were about to turn things around.
Griffith hadn't conceded a point in the last month, but Cleland thought Wagga City's defensive effort was the real key.
"I've been telling the girls from the start that we have plenty of points in us but our defence can leak a few too many so we spoke before the game about actually stopping them from scoring the tries," Cleland said. "We were able to go a long way."
He also believes the hard work Allcorn has put into her conversion attempts is really paying off.
Apryll Green, who bagged a double, and fellow tryscorer Kate Pevere were among the best for Wagga City.
With a clash against third-placed Albury on Saturday, Cleland hopes the win will be a massive boost for the side heading into finals.
Wagga City's surprise win makes things tougher for premiers Ag College to secure their finals berth.
Despite a 55-0 win over Leeton, they are now four points adrift. CSU are a further six points back after a 50-0 win over Hay.
Waratahs also posted a big score, taking a 51-0 win over Tumut ahead of their clash with Griffith on Saturday.