The group realised they had gone the wrong way when they arrived in Tauranga about the time they should have arrived at Waitomo.
An hour later the friends, who had come to New Zealand to study in Auckland, were able to return to Auckland on the bus they had arrived on.
Emma said she complained to the company by email three days ago but had not received a reply.
Emma hoped the company would refund the roughly $90 each woman paid for the return trip, but said it wasn't just about the money.
"I want them to really think about why their system is not complete."
She feared other travellers might also have suffered a similar fate.
Emma said she was disappointed not to have seen the Waitomo Caves and still hoped to visit but said she was unlikely to book a bus trip.
Nakedbus said it was unable to comment yesterday.