Leslie McDonald, 51, was charged Friday with criminal negligence causing death and failing to provide the necessities of life.
Her grandson, Maximus Huyskens, died on June 26, a month before his second birthday.
He was laid to rest Wednesday in an emotional service that drew family, friends and even some strangers.
Rev. Peter Tuyen Nguyen, who led the funeral mass, called the toddler's death a "freak accident" and called on those gathered to support Max's parents and his two older siblings.
Police have said the boy died after "being exposed to high-level temperatures for an extended period of time" in a sedan outside a Milton, Ont., home.
Investigators have said the child was in the care of his maternal grandmother while his father was at work and his mother was at an appointment.
McDonald is scheduled to appear in court Aug. 14.
Meanwhile, police in Edmonton have ruled no crime took place in the death of a little girl found inside a car during a heat wave this week.
Police say the three-year-old girl was not left in the car by a caregiver on Tuesday evening. Officers did note that the vehicle she was found in was not locked, but didn't provide any further detail about how she got there.
Hamish Stewart, a criminal law professor at the University of Toronto, said intent doesn't factor into prosecuting someone for criminal negligence.
"The crown has to show that it was a marked and substantial departure from what a reasonable person would do in the circumstance," he said.
A simple mistake or brief oversight would not meet the definition of criminal negligence regardless of the severity of consequences, Stewart said, but a serious mistake would fit the criteria.