The devastated mother has made a desperate plea for information after her daughter went missing a month ago, as police continue to hunt for answers.
Trisha Graf, 41, was last seen driving near Andamooka, in South Australia's far north, on December 12.
SA Police, who declared the case a major crime on January 6 and are treating it as suspicious, combed the area on Tuesday.
But Ms Graf's mother, Anne, who lives 600km south of Andamooka in the Barossa Valley, doesn't believe Trisha would leave her children 'in a million years'.
'There's no way Trisha would have left them willingly, especially so close to Christmas and with Lily's 11th birthday coming up on the 19th,' she told The Advertiser on Tuesday.
'Trisha was a big girl. You'd have to have someone else involved.
'The bad thing is there's that many mines out there I don't know if police will be able to find her.
'They're going to have to be smart about it. I do think she's been left in one of those [old shafts].'
Trisha moved to Andamooka from Cadell last year with her partner and their two children, 10 and 12. She also has four adult children.
It is understood the two young children were at a friend's home on the night of their mother's disappearance.
Anne Graf has made an appeal for anyone with information to come forward.
'We need answers and her kids especially deserve to know why their mum isn't with them,' she added.
SA Police will conduct door knocks around Andamooka on Wednesday, focusing on several locations where Ms Graf was last seen.
'We have established Trisha's movements on the evening and morning she was last seen,' Detective Superintendent Darren Fielke said on Monday.
'But we believe there are people who may have seen her within the town who have not yet contacted police.
'We know there were people who were with Trisha at both the Roxby Downs Hotel and who saw her after she returned to Andamooka and we need to speak with them.'
Ms Graf's mother fears her daughter would not willingly leave her children.
Ms Graf was last seen at the Roxby Downs Hotel at 12.19am on December 12, leaving a short time later in a white 2012 Ford Territory (SA registration S254BCX), accompanied by a friend.
She drove towards Andamooka, colliding with a kangaroo just outside the township.
Despite the accident, Ms Graf and her friend continued into town and visited a house in the north-western area.
Shortly before 2am, Ms Graf left that address to make the short trip home. She was last seen driving along Dunstan Drive in Andamooka.
Just after midday on December 12, Ms Graf’s partner and a friend, who were searching for her, found her Ford Territory perched on a dirt mound near the Blue Dam, east of the township.
The vehicle had sustained damage from the collision and could not be driven from its position.
Police and SES initially conducted ground and aerial searches, followed by a community search in Andamooka.
Police divers later searched the Blue Dam, but Ms Graf was not found.
Since then, police from the Far North, Port Augusta, the Missing Persons Section and PolAir have carried out further ground and aerial searches.
A community page stated Ms Graf was wearing black pants and a black top at the time of her disappearance.
Her hair was also up in a plait, away from her face.
Ms Graf is known to have a nose piercing, lip piercing and ear piercings as well as a skull tattoo on her upper right arm and a mermaid tattoo on her lower forearm.
Anyone with information about Ms Graf's whereabouts or her movements leading up to her disappearance is urged to contact Crime Stoppers on 1800 333 000.