Ryszard Krawczyk had met the 48-year-old in the Maggs Day Centre in Worcester for the homeless in 2009 and later lived in an adjoining flat in Gresham Road, Dines Green, Worcester.
She had let him use her washing machine and he told how he had seen her walking hand-in-hand with William Cummins, the 51-year-old known as Birmingham Billy, who has been accused of her murder.
Cummins, of no fixed address, pleads not guilty to killing her at her flat between March 16 and April 13.
Her battered and decomposing body was found by police after neighbours became concerned about her welfare.
Mr Krawczyk, currently serving a prison sentence for shoplifting, confessed he was an alcoholic and knew that Jackie also liked a drink. They would often have a social drink at her flat.
When he had seen her and Cummins walking in the Meco Alley in St John’s, Worcester, they were like girfriend and boyfriend. He realised it was an up-and-down relationship and knew of one dispute when she claimed Billy had cut her hair.
The witness had lived in Gresham Road since September last year and Jackie had let him use her washing machine several times.
Cross-examined by defence counsel Richard Benson QC, Mr Krawczyk agreed that security of Jackie’s flat was not good.
The front door was often on the latch and sometimes a block of wood was jammed in a back door to keep it open.
He did not know that Jackie was an epileptic and suffered from seizures and had once fallen down stairs.
But he knew she was terrified of a neighbour who lived 100 metres away and she alleged he had raped her. “He was an intimidating guy, unpredictable in drink,” he said.
Mr Krawczyk said there were often many visitors to his flat and there had been drunken parties.
On one occasion, a Polish friend, who was now in his native country, had punched Jackie in the face knocking her to the floor after an argument. Jackie also had another boyfriend, named as Sam, and he was very jealous and threatened anyone who went out with her while he was in prison.
He had once poured boiling water over her.
Mr Krawczyk said Jackie could also be jealous and aggressive.
She had once been involved in a cat-fight with his girlfriend and it ended with them both pulling each other’s hair.
Jackie also became annoyed when Billy, who often wore a pink dressing gown in the flat, had started to change in front of a girl visitor.
There had been a drunken gathering at his flat on the day of Jackie’s funeral and it ended with one guest punching and kicking another.
Tanya Frankum was also a visitor at Mr Krawczyk’s flat one day when Jackie burst in distraught.
She said Billy had beaten her up and had been smashing plates in the kitchen.
He locked her out and Miss Frankum had to climb round the balcony to get in through the back door.
Mr Benson, who had asked about the number of men visiting Jackie, told the jury that he had not intended to make a personal attack on her character.
PC Lee Palmer, who was on duty at the flat when the body was discovered, said he had been approached outside the door by a man identified as Lee Telford, who claimed he had heard “Billy from Birmingham strangling Jackie”.
The trial continues.