She had popped out to pick up an older child from school and had left the toddler with her 25-year-old uncle who was sleeping inside.
At some point after she left, the child has walked outside and onto the road before meeting the stranger who then helped her back to the house.
The grandmother confirmed the male relative was not made aware he was now the only adult in the house.
"I apologise on behalf of my daughter's actions. But she didn't deliberately do it. It was just a mistake ... she didn't mean to do it.
"And now it's gone as far as it goes like she's one bad mother.
"She's got a 7-year-old son. Nothing has happened to him ever since he was born. Now the little girl is nearly 3 years old and this is the first time something like this has happened to her.
"It's just a careless mistake that she's made because she was rushing. But the bottom line is, people are taking it, twisting the story and taking it as far as it goes. They blew it up.''
The grandmother said other family members were now supporting the mother while she looked after her children in the meantime.