The 18-year-old disappeared as she walked to her parents' house in Coventry in December 1991. Her body has never been found.
Nigel Barwell and his brother-in-law, Thomas O'Reilly, deny her murder.
Marilyn Payne said Nicola was looking forward to Christmas in a new home with her partner and son.
"She would never have left her son," she told jurors at Birmingham Crown Court.
The court has heard Miss Payne's family received a number of anonymous phone calls after her disappearance.
Marilyn Payne said they were made by one person, whom she described as being "very vicious".
Prosecutors allege Miss Payne was abducted and murdered as she crossed wasteland known as the Black Pad in Coventry.
Mr Barwell, of Copperas Street, and Mr O'Reilly, of Ribble Road, Coventry, are now aged 51, but were both 27 at the time of her disappearance, on 14 December 1991.
In evidence, Miss Payne's father, John, said it was unusual for her to walk to their house.
He told the court he first called her boyfriend, Jason Cook, when his daughter did not reach their home and then started to search for her.
The trial continues.
The mother of missing Nicola Payne has told a murder trial her daughter was a devoted mother who would never leave her young son.