Fiji's performances have put the Jillaroos on alert ahead of their World Cup semi-final on Sunday.
Fiji beat Papua New Guinea 40-4 and France 54-6, and pushed New Zealand before losing 18-12.
"We know that Fiji did put in quite a fight against New Zealand," Jillaroos winger Abbi Church said.
"We know they're going to come out this week and we have to obviously be prepared for that".
Coach Jess Skinner said Fiji's confidence and underdog mentality would make the match challenging.
"They've had an outstanding campaign, and what they did to the Kiwis put the rest of the competition on notice."
Australia booked its semi-final spot after beating Wales 124-6 on Sunday, the biggest margin of victory in international women's rugby league history.
Jaime Chapman scored six tries, equalling the Jillaroos record for most tries by one player in a game.
The result followed Australia's 78-0 win over England and 40-0 victory against Samoa, but Church said the team was still looking for improvements.
"No performance is perfect, and there's always things that we can improve on," she said.
"(We) reflect on the own performances and be quite critical and look to where we can improve individually and as a team."