Medical treatment was needed at the scene for three people, St John spokesman Gerard Campbell said.
Firefighting crews from Wanaka, Lake Hawea, Alexandra and Luggate extinguished the blaze.
A shaken Miss Stewart told the Otago Daily Times yesterday afternoon she was relieved everyone had got out alive.
The fire had brought into perspective the importance of family, she said.
"Make sure they are the first thought every day."
The families had received amazing support from the community, including from the Wanaka Skate Club and retail shop Cheapskates Wanaka, she said.
Fire investigator John Smalls said the heat of the fire might have approached 1000degC. It had certainly exceeded the melting point for aluminium, 660.3degC.
He would carry out interviews today and another investigator would help him tomorrow.
Wanaka firefighter Tony Wellman said the house Miss Stewart was living in was engulfed in flames when firefighters arrived.
The house had been built with modern materials and they burnt quickly, he said.