The Kiwi Ferns will meet Fetu Samoa in a semi-final in Newcastle next Saturday after beating the PNG Orchids 40-12.
Played in slippery conditions at Cbus Super Stadium on Saturday, the match was tight at half-time, with New Zealand ahead 14-12.
Stacey Waaka, Mackenzie Wiki and Kaiyah Atai scored for the Ferns before the break, while Tia Molo and Elsie Albert crossed for PNG.
Otesa Pule opened the second-half scoring with a solo try from 50 metres, just 35 seconds after play resumed.
Wiki scored again in the 46th minute, extending the Ferns' lead to 24-12.
Leianne Tufuga then finished a move involving Nicholls, Atai and Abigail Roache, who later scored herself to make it 34-12.
Atai set up Roache's second try in the 63rd minute, as New Zealand continued to pull away.
The Ferns' back five of Nicholls, Tufuga, Roache, Waaka and Wiki made 68 runs for 795 metres and contributed six tries.
The other semi-final sees the Jillaroos face Fiji Bulikula in Sydney on Sunday.