Australia and New Zealand have a longstanding agreement to remove quarantine obligations on travellers, dating back to May last year.
Eastern Australian states have fulfilled their side of the deal, allowing Kiwis to bypass the otherwise mandatory fortnight of isolation.
New Zealand is yet to do so.
Ms Ardern is holding back out of an abundance of caution, following her country's health-first approach to fighting Covid-19.
However, in recent weeks, the calls from separated families and tourist-starved businesses are becoming stronger, urging Ms Ardern to allow for more leniency towards travel.
The arrival of vaccines in Australia has Scott Morrison's government looking towards other countries to restore pre-Covid travel normalities.
On Sunday, Deputy PM Michael McCormack told the ABC of its goal to open to Singapore "potentially for a bubble in July".
Ms Ardern, following her Fortress New Zealand mantra, said that could set back trans-Tasman travel.
"If Australia makes the decision to open up, and we think that that poses risks to us, then we will reconsider," she said.
Ms Ardern told Radio NZ that New Zealand is not interested in joining the Singapore bubble - yet - as it focuses on Australia.
"Australia is the country that most closely mirrors both our strategy and our management at the borders," she said.
Still, she has been repeatedly unable to demonstrate progress towards that goal.
Ms Ardern points to a spree of issues that are yet to be negotiated before a trans-Tasman bubble can be formed, including transit arrangements, eligibility, and protocols in the event of outbreaks.
"At the moment you don't hear a lot of people raising issues about being stranded," she said.
"But I can guarantee if we had a two-way quarantine-free arrangement, we would certainly hear if we had issues in Australia that caused us to take a pause and shut down flights.
"So we need to be prepared for how we would manage that, particularly if people needed to get home."
