Australia misfired with their opening kickoff, allowing Ruby Tui to go on a big run. But Ellia Green quickly got Australia back into the match, smashing Niall Williams to win a turnover and then going on a long run for a try.
Green, whose match play had been limited to keep her fresh for the big games, was required again soon after, cutting down Dhys Faleafaga who was threatening along break.
Tyla Nathan-Wong then set up a Hirini try, giving the Black Ferns a 7-5 lead. A clever switch presented Williams with a try late in the first half, with Charlotte Caslick again caught out on defence.
With the halftime hooter having sounded, Australia launched a long-range move down the left, with Emma Tonegato keeping Kelly Brazier at bay for the try.
Final player of the match Nathan-Wong blew the opening second-half kickoff handing Australia the initial advantage, but they were saved by an Aussie knock on. And Nathan-Wong struck with a 60 metre try to send New Zealand to a 21-10 lead, and well on the way to victory.
A great breakdown steal by Hirini looked to have got New Zealand home but Green grabbed a brilliant intercept try. That left Australia with under 10 seconds to overturn a 21-17 scoreline but they could not grab the kickoff cleanly and were unlucky with a knock on call.