Meanwhile, 17 bodies had been recovered after an avalanche triggered by the quake buried part of Mt Everest's Base Camp. The death toll is expected to rise.
Ms Gillbanks' mother, Carol Waghorn, said her daughter was walking down a street with a friend about 11.45am local time when the quake hit.
"She said it was pretty horrific.
"She was walking down the street and felt this big rock, and she grabbed her friend and pushed her up against the wall under some roofing. Her friend thought it was a bomb going off.
"They saw everything crumbling around them and people being buried."
The quake's epicentre was 80km northwest of Kathmandu, and it had a depth of 11km, which is considered shallow in geological terms.
The Kathmandu Valley is densely populated with nearly 2.5 million people, and the quality of buildings is often poor.
That night the Woodford House old girl and her friends were forced to sleep in the street because their hotel was no longer structurally sound.
The city shook with tremors all night, she said.
"They had a really big one at 5am. She said it was really scary and all the dogs were barking."
Ms Waghorn initially learned of the quake watching a news bulletin on television in her Havelock North home.
"It came up on the TV.
"We were watching the rugby and there was a breaking-news flash saying there had been an earthquake in Nepal. I said, 'Oh no ...' I was just beside myself. Three minutes later I got a text from her."
It had been a lifetime dream for Ms Gillbanks, now based in Perth, to visit Mount Everest.
She was staying in Nepal with four friends and had planned to begin climbing the mountain in two days.
Now she was desperate to leave Nepal, but the airport was congested and there was an indefinite waiting time to leave the country.
"They're desperate to get out. They're just over it.
"It must be awful, seeing all the bodies, and seeing the people who were trapped in buildings.
"I just want her out of there - with all these aftershocks, the buildings are still crumbling."
Yesterday the Ministry of Foreign Affairs and Trade (Mfat) confirmed the well-being of about 110 New Zealanders in Nepal.
A statement from Mfat said the New Zealand High Commission and Honorary Consul in Nepal continued to seek information about the welfare and whereabouts of any New Zealanders in the affected area.
Communication networks in the affected area, including in Kathmandu, had been disrupted following the earthquake, making it difficult to contact New Zealanders, Mfat said.
The Nepalese Government has declared a state of emergency in affected areas and appealed for international assistance after the quake destroyed homes, businesses and temples in Kathmandu and the densely populated surrounding areas.
