What followed was the ''worst night'' of her life, she said on Instagram.
When they realised the ''horror'' of the scene they encountered they ran to the water and attempted to save the whales.
They desperately grabbed the whales' tails before getting ''hammered by them thrashing around''.
''It was useless - they were so big and heavy and the realisation we could do nothing to save them was the worst feeling I've ever experienced.
''We were in a place with no people, no service, no help.''
Seeing and hearing the whales while not being able to do anything to save them was heartbreaking, she said.
''I'll never forget their cries, the way they watched me as I sat with them in the water, how they desperately tried to swim but their weight only dug them deeper into the sands.''
She said one of the group was able to contact the Department of Conservation after running 15km back to the base hut.
And while saving the whales would have been impossible, getting the message to Doc spared the whales more misery as they were euthanised shortly afterwards.
''Otherwise it would have likely been days before anyone even knew the whales were there and a very long, painful, slow death for them all.''
She said she would ''never be the same'' after seeing the whales.
Doc Rakiura operations manager Ren Leppens said about half the whales had died by the time they were discovered, and the remaining whales had to be euthanised.
''Sadly, the likelihood of being able to successfully re-float the remaining whales was extremely low. The remote location, lack of nearby personnel and the whales' deteriorating condition meant the most humane thing to do was to euthanise.''
Te Runanga o Awarua chairman Dean Whaanga said a rahui (restriction) would be placed over the whales.
''The intention of a rahui is to deter people from going near the whales as they decompose, primarily for their own safety.''
