Centre Samantha Sinclair and goal defence Katrina Grant pulled off turnovers - the latter capping an exceptional game as captain - allowing some breathing space over the closing minutes.
New Zealand stole the Quad Series last year when they thumped Australia in their last game to win the tournament on goal difference despite a loss to England.
In theory they could repeat that by beating Australia again in the final match of this series. But shooting star Folau said the focus goes beyond their next match.
"I'm not here to win a Quad Series, I'm here to learn and be better for the Commonwealth Games," Folau told the Weekend Herald.
"We know that we've got a long way to go and Sunday's another learning experience for us and how we can be better for the Commonwealth Games, because at the end of the day that's the bigger picture that we are aiming for."
Folau said the Ferns had taken the positives from their loss to England, which saw them give up a three-quarter time lead to lose in overtime.
Concerns were quickly raised about the Ferns' ability to perform under pressure during critical moments, but Folau said playing in the Quad Series was going to be about "growing from the tough situations".
"We've just got to learn and the only way we're going to learn and grow is when we're put through these tough times," she said.
"I felt that yes we lost against England, but in saying that, we played some stuff in that game that we had never done before, not even at training.
"We always want to win but, most importantly, as long as we are growing and progressing as a team and as individuals and how we can be better each time we go out on the court, and if it's going to make us be the best that we can in the Commonwealth Games in April, we'll be sweet."
The Silver Ferns face Australia in Johannesburg at 11pm (NZT) tomorrow.
