The girl's mother, a 36-year-old woman from Milton, was driving the SUV northbound when she lost control, entered a ditch and hit the hydro pole. The woman was treated in hospital for minor injuries.
The girl succumbed to her injuries at Milton District Hospital.
Halton Regional police said blowing snow may be part of the cause of the collision. Both the driver and passenger were wearing "their appropriate safety restraints," police said.