Cooper had been caring for four of her daughter's children at the time of Jermain's death, all of whom were pre-school age.
Jermain's mother Nadia Ngawhau told the court this morning she was "very disappointed, very sad" and "quite upset" that CYF had removed her children and placed them with Cooper.
"Me and [my partner] at the time were going through some rough patches, with him being a bit violent and kinda scaring me a bit. I was pregnant and ready to go into labour and everything just hit me all at once and I just had a major breakdown," she said through tears.
She said she would visit her children and help her mum, mostly on the weekends.
"Helping her with preparing her dinners, helping her clean up and tidying up after the kids, helping with their birthday parties, helping with any assistance she needed with the children I would be there to help her.
"I had a breakdown and I couldn't cope with looking after my children, I did have seven children at the time," she said.
She said her relationship with her mother was "great", and from what she saw her children loved their nana.
"They loved her, it was always nana this and nana that, and I'm thinking 'I'm still your mother'," she laughed. "But they loved her dearly, absolutely."
She said when her children were disciplined by Cooper it was "in a good way, not in a bad way".
"It was always in a good way ... Just keeping them on track.
"I'm so thankful to my mother that she had done that. She was trying her best for them."
She said the discipline could include a ban on "treats" such as ice cream, but never witnessed any physical discipline.
"There was no anger or aggression towards them - they would listen, it was just how my mother spoke."
Ngawhau said she wasn't at her mum's home the day her son was injured, but said Cooper rang her after calling an ambulance.
"She told me, as far as I know, she was with the kids watching a movie," she said, recalling the mid-December day.
"Nana, Nana wake up," Ngawhau explained her mother was told by one of the children.
"She had discovered Jermain in the hallway and she had rung an ambulance and then tried to ring me."
Crown prosecutor Aaron Perkins QC told the jury yesterday that Cooper insisted she had phoned for an ambulance first after discovering Jermain's injuries.
"But she didn't, members of the jury, that is very clear from the telephone records," he said.
When emergency services arrived paramedics determined the toddler needed immediate surgery, Perkins said.
"He had a severe head injury, emergency surgery was performed at Starship [Hospital], but there was no hope - the injuries were too severe.
"The damage had been done.
"A very bleak picture, indeed."
