Josie Mahon, 27, identified the blue-and-white top with its "Thomas the Tank Engine" design as the one she had dressed Rosemary in before leaving her with babysitters on the night before the girl disappeared.
Ms Mahon was visibly upset as she quickly glanced at the top before turning away in the witness box at Manchester Crown Court, where her former boyfriend Andrew Pountley, 32, is accused of Rosemary's murder.
The Crown alleges that Mr Pountley, of Kew Road, Oldham, a pub disc jockey, argued with Ms Mahon that evening and threatened to kill her.
It is claimed that he took a taxi to Ms Mahon's home in Kipling Road in the town.
Rosemary had been left sleeping alone there with her six-year-old brother. The court heard that Ms Mahon arrived home after midnight. The baby-sitters left but Ms Mahon went to visit a neighbour a few doors away, leaving the children with the front door closed but not locked.
The Crown alleges that Mr Pountley took Rosemary from her bed in the early hours and took her to his own home where he then raped and suffocated her.
Mr Pountley pleads not guilty to the abduction, rape and murder of the girl a year ago.
Ms Mahon, a mother of three, told the court how she met Mr Pountley nearly three years ago and moved into his home. But she said he became jealous of her.
"He would behave very violently. There were quite a few arguments. He would always be accusing me of looking at men in pubs and flirting," said Ms Mahon. "I left because he got too violent altogether."
She said they later restarted their relationship and he would stay at her home sometimes two, three or four times a week.
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