Thanks for the responses. In the end I called NZ Immigration and they confirmed my wife needs an ETA. Just yesterday, 4 days before our flight, Qantas sent an email mentioning this, otherwise nowhere in the booking process was it mentioned. I can imagine many panicked passengers being informed at check-in that they can't travel!
Anyway we got the ETA within a day so are set. I'll query the check-in staff about this and report back too. Seems like QF should inform of this earlier in the process since logically most passengers transitting would not expect the need for a visa.
The NZeTA is not a visa. Some people would require a transit visa.
https://www.immigration.govt.nz/visas/?page=1
Some people, including citizens of Visa waiver country or territory can travel to New Zealand with a New Zealand Electronic Travel Authority (NZeTA) instead of a visa. You do not need a Visitor Visa or an NZeTA if you are an Australian citizen travelling on an Australian passport.
Check if you need an NZeTA or visa
You cannot work in New Zealand on a Visitor Visa, however, you may be able to work remotely for an employer or client based outside New Zealand.
Tell us if family members are travelling with you and have applied for their own separate visa. Write a letter that includes each member's full name, date of birth, passport number, and visa application number if known. Include the letter in your visa application.
Just as some-many people visiting USA need to apply for a
"visa waiver"
https://travel.state.gov/content/tra...r-program.html
Have read of reports of people applying for NZeTA when trying to check in.