The accident was "truly sad", the judge said.
Singh was driving in difficult road conditions with his mother, who was visiting from India, and his three-year-old niece, who was not properly restrained.
He lost control of his van, which rolled at about 40km/h. His mother died at the scene. The injured little girl was flown to Auckland's Starship Hospital.
"The consequence of a minor omission led to the magnitude of what we see here."
The maximum penalty of three months imprisonment was indicative that the law understood such things happened occasionally -- even when the driver's fault was very minor, Judge Adeane said.