In sapping conditions in Port Moresby on Saturday, the Bulikula defied a vocal home crowd at Santos National Football Stadium to race out to a 30-4 halftime lead.
The Fijians piled on a further two second-half tries as winger Tahlia Marshall brought up a hat-trick to record the biggest win in the team's history.
The Bulikula will head into next Saturday's meeting with minnows France on the Gold Coast, knowing a win will secure their place in the knockout stages.
After narrowly losing to New Zealand last week, Fiji proved they would be no pushovers and it took just four minutes for the Bulikula to take the lead through Sienna Laing.
And while crafty Orchids hooker Ua Ravu quickly hit back for PNG, the floodgates soon opened for the Fijians.
Five-eighth Luisa Yaranamua barged her way through some exhausted defenders and then the 20th-minute introduction of barnstorming bench forward Lorren Ieli put Fiji on track for victory.
Ieli ripped through the PNG middle in 15 minutes leading up to halftime with Taina Naividi, Losana Lutu and Marshall all crossing to heap more misery on the Orchids.
Marshall added two more after halftime as Fiji kept the Orchids scoreless in the second half.
The result leaves PNG needing a minor miracle against the Kiwi Ferns on the Gold Coast next week to stand any hope of making it out of the group stage.
New Zealand have never lost to the Orchids and, even if they did, the heavy loss to Fiji and the impact on for and against would scupper PNG's hopes of making it to the knockout stages for a second successive tournament.
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