The next-door neighbour gave the alarm about 12.40am on Sunday morning after her daughter had heard glass crackling in the small building close by.
The Mangaweka, Hunterville and Taihape fire engines and the Marton tanker attended. They were there for nearly three hours.
The neighbour, who did not want to be named, said she was hosing her own house down to keep it cool. It was raining at the time of the fire, with no wind.
Ms Moon's home was completely destroyed in the blaze, Mangaweka chief fire officer Rex Noble said.
A caravan on the property and trees around it were also scorched, although Ms Moon said she would have to live in the caravan temporarily.
Her father, Lionel Moon, owned the house and lost thousands of dollars worth of property.
Mr Moon, who lives two doors down from his daughter, has been in Ohingaiti for all of his 81 years. He didn't know about the fire until Sunday morning.
Ms Moon had been living in the "bach" for years, though this year she has been away since June, working in a shearing gang in the South Island.
The building was not insured.
Asked how he felt about it, Mr Moon said: "Not too good."
He said fire investigators and police were at the scene on Sunday. The fire investigator told him he wasn't sure whether the fire was deliberately lit or caused by an electrical fault.
Mr Moon said their were some "bad eggs" around who hated his daughter.
Whanganui CIB are still investigating the fire, Senior Sergeant Andrew McDonald said.
