Ellie-May Minshull Coyle died after allegedly having been tied face-down on her mattress, which was surrounded by cot sides covered with blankets and towels.
Her mother, 19-year-old Lauren Coyle, is one of three people charged with manslaughter – along with her partner Reece Hitchcott and their lodger Connor Kirby, both 20.
Coyle told the court that Ellie-May, who was 19-months-old, was lying on her back and unrestrained when she put her back to bed after she woke up at about 7am on 23 March last year.
Liverpool Crown Court heard that she fell asleep on the sofa soon after, only to wake when her father, Sean Coyle, visited the two-bedroom flat in Preston at about 9.25am.
He went into the bedroom to check on his granddaughter with Hitchcott, but rang emergency services when he realised she was not breathing.
Coyle told the court that when Hitchcott took Ellie-May out of the purple Disney bed, she noticed what appeared to be a black Velcro strap around her ankles.
She said: “I said to Reece: ‘Did you do this? Why would you do it?’ And he said: ‘I’m sorry.'”
Coyle also claimed that the bed was converted by Hitchcott.
“I did tell him that I didn’t like it but I never told him to take it down,” she said.
“I asked Reece what it was for and he said ‘give it a couple of weeks and Ellie will be in a routine and settling’, so I just took his advice.”
“I should have stood my ground and got Reece to take the bed down.”
Coyle described her daughter, who she had with ex-boyfriend John Minshull, as her “world”, but in a text message sent to Hitchcott revealed that she had “smacked her loads”.
She told the court the toddler would have tantrums and bang her head off the floor and doors when she did not get her way- and the text message referred to her smacking her on the back of the hand once or twice following those tantrums.
In another text, sent on 8 March last year, she told Hitchcott: “I literally just feel like jumping in front of a train.
“I just feel down with this child constantly being naughty and I’m so stressed out it makes me feel dizzy.”
And in one sent nine days later, just a week before the death, she said: “That child’s f***ing woke me up screaming the whole flat down banging her head. Feel so knackered.”
Following the death, a postmortem found that Ellie-May had died due to “forcible restraint by ligatures in a face-down position complicated by hyperthermia”.
Coyle, Hitchcott and Kirby have all pleaded not guilty to charges of manslaughter, causing or allowing the death of the child, child cruelty by “caging” the child in her bed, and another count of child cruelty by restraining her in the bed.
The trial continues.