"It's shocking.
"I could have gone to Australia and back."
Adding insult to injury, there were plenty of empty seats going begging when she boarded the flight.
"That's what made me really mad."
The experience left her worried for others who could not afford the fee and how put out they would have been, she said.
Bartlett said she had flown with Jetstar before and had never had any problems with their service in the past but admitted she probably would not want to fly with them again.
She had been told she would receive a refund, but was yet to hear from the company about when it would be made.
A spokesperson for Jetstar said Bartlett had "mistakenly booked the wrong date for her return flight and did not realise until arriving at the airport".
"We understand this is an easy mistake to make in February and March as the dates and days of the week are the same in both months.
"To assist customers, we have a special policy in place across all airports to move customers to alternative flights free of charge if they have made this error," the spokesperson said.
They apologised "as this should have been offered at the airport in line with our policy and we will be in contact to refund the additional flights".
The "special policy" had been adopted because the days of the week in February fall on the same day as those in March, meaning airlines experienced a higher rate of booking errors from customers.
Bartlett was recently presented with her New Zealander of the Year award by Prime Minister Jacinda Ardern.
The award's chief judge, Cameron Bennett, said Bartlett's "enormous personal sacrifice" had changed the lives of thousands of New Zealand's lowest-paid workers who provided vital health and wellbeing services to many vulnerable Kiwis.
"Kristine embodies the values of fairness, decency and equity that New Zealanders have long held dear.
"She didn't seek out admiration or special recognition for what she helped achieve. She saw a need and had the courage of conviction to take action. That makes her a thoroughly worthy recipient of this year's supreme award."
Previous winners of the award include Hunt for the Wilderpeople director Taika Waititi and former All Blacks skipper Richie McCaw.