A court heard the youngsters were crying and distressed when officers found them in the dark with limited food in the house at the property in Wakefield.
Leeds Crown Court heard police went to the property at 4.50am after receiving information that children were alone in the house.
The officers looked through the letter box to see the house in darkness but could hear one of the children whispering "Mummy".
Another child was then seen crying at the window.
One of the children said to the officers through the letter box: "It's dark and I don't know where the key is and Mummy has gone."
Officers managed to gain entry to the property to find two of the youngsters sobbing.
The youngest child was asleep downstairs under a duvet.
The oldest child, aged nine, said he had been told by his mother that he was old enough to be left alone to look after his siblings.
There was little food in the freezer.
The children said they had been given soup and bread by their mother the previous evening.
The mother returned to the property an hour later.
She claimed she had not left her children on their own but had been outside for a cigarette.
The defendant admitted the offending after being shown CCTV footage of her alone at a garage several miles away hours earlier.
She pleaded guilty to four counts of causing unnecessary suffering to a child.
Recorder Joanne Kidd deferred sentencing the woman until probation reports and further information could be obtained about the defendant.
The court heard she had been homeless since that offence and had not been able to be contacted by authorities.
The woman will be sentenced on August 6.