Northcroft - an associate producer on TV series Vegas - said her adult children usually lived in the Glenholme house, but they were away for a New Year's break. Her sister was house-sitting with her dog and was inside when the fire started.
She made it out safely with the help of a neighbour. Her dog hid under the house and managed to survive "somehow," Northcroft said.
Northcroft said the fire started in the sleepout, spread to the carport, and then the house.
She was notified of the fire at 11am.
"The fire service were so awesome, they got there so quickly," she said.
She said she and her family had "lots of good support on the ground" from their friends, family, and the community.
"My priority was making sure my family was okay and getting them out of there, because it can be kinda distressing watching that happen."
At this stage, she said the cause of the fire was unknown, although there were suspicions it may have been electrical.
"Not a nice ending to the year, but it's been a pretty s*** year anyway. See you later 2021."
Five fire trucks from Rotorua and Ngongotahā were called to the Seddon St blaze.
There were fears the neighbouring house may have also been in danger, a Fire and Emergency spokesman said.
Shortly before noon, Rotorua Fire Brigade senior station officer Tony Kelly told the Rotorua Daily Post it had taken about 20 minutes to bring the fire under control.
He said when he was at the scene there were many people gathered but he could see police helping to clear them, as well as closing both ends of Seddon St.
Kumar said Ranolf St and other nearby side streets were "in a jam".
Just before 11.30am, a woman at the scene who wished to remain anonymous said she had been there for about 10 minutes and saw some smoke and flames.
However, she said it appeared the fire brigade had it under control when they arrived.
She said she was worried about her tenants living in the house next door and there may be more damage to the side of the property than she first thought.