Police used DNA testing to determine the identity of the child's biological father.
A NSW mother accused of murdering her daughter went through a dramatic change before she abandoned her sons and moved away, a court has heard.
She also abruptly ended a close friendship "out of the blue" several years before the girl was born, the former friend told her trial in the NSW Supreme Court in Newcastle.
Raelene Gannon on Wednesday said she and the woman, who can't be named for legal reasons, had a "normal" friendship for a couple of years when they both lived on the Central Coast in the 1990s.
Their sons were roughly the same age and the women often went shopping together or caught up at home, Ms Gannon said.
But one day she arrived at her friend's house to find a woman she'd previously never heard of had moved in, taking one of the children's bedrooms.
"I didn't know anything about her of where she came from but it just struck me as unusual," she said.
"Whatever year that was, that was when things changed."
Some months later the woman answered Ms Gannon's knocks on her door and said she didn't want to see her again.
"I just said why, because it was out of the blue," Ms Gannon said.
Ms Gannon said she spoke with the woman a handful of times in the years after their friendship ended, and was aware she'd been hospitalised for mental health issues.
The court heard the woman later abandoned her sons, leaving them in the care of her mother and moving interstate.
She has pleaded not guilty to murdering her toddler daughter between Christmas 2000 and Christmas 2001 when she had moved back to NSW.
The girl has never been found and the woman has allegedly told people she is alive, safe and living with another family.
The woman's mother previously told the court she ran into her daughter on the street in 1998 after she had moved back to the area and tried, unsuccessfully, to regain custody of her sons.
She was wearing long flowing robes and a pentagram and said, "you'd better be careful now, I'm a high priestess".
She and Ms Gannon both said they never met the missing girl, who was born in 1999 and would be turning 18 this year.
Defence barrister Tim Gartelmann SC previously told the court the Crown's case was circumstantial down to the basic fact the girl was dead.
He said that if she did die, there was no evidence to show how.
The judge-alone trial was adjourned early on Wednesday after several witnesses were affected by a medical emergency.
It is expected to continue before Justice Robert Allan Hulme on Thursday.