As Ms Dargusch watched on, two of the group jumped from a ledge near the track down into the water hole, about 7m below.
"She appears to have lost her footing and fallen on to a large slate of rock below," said Senior Sergeant Rupert Friend.
Ms Dargusch was airlifted by rescue helicopter to Waikato Hospital's Emergency Department and from there she was transferred to the ICU. She died on Saturday, a week to the day she suffered the fatal injury.
Until the accident Ms Dargusch had been posting photographs of her New Zealand trip on Instagram, including shots of sunsets, beaches and native bush.
Ms Dargusch had been working as a receptionist for Brisbane's Alpha Physiotherapy. Her boss, Scott Hewett, posted a tribute on Facebook.
"My heart goes out to you Ashleigh Dargusch. Our clinic will never be the same without you and you will be greatly missed. Rest in peace, you beautiful girl. We will never forget you," he wrote.
A tribute also ran on the company Facebook page. "She was an extremely valuable member of our staff and will be greatly missed. Our thoughts are with her boyfriend Jared and family during this difficult time."
Her friends were shocked by her death. "Rest easy beautiful girl. You'll be so missed. I feel devastated that this world is now without you," Emma Bradbury posted on Instagram.