A mother twice left her seven-year-old daughter home alone at weekends - once with just cake and juice - while she visited a boyfriend in London.
She told the youngster she was "going a long way away" and not to touch anything dangerous or the computer, a court heard.
The woman locked the girl in their flat in Knighton, Leicester – and was only caught after concerned neighbours alerted the police.
Leicester Crown Court was told the police broke in to the property to rescue the child in July 2014.
All she had been left was "juice to drink and some cake," said Philip Gibbs, prosecuting.
The little girl and two younger siblings - who were not locked in the flat - are now all being cared for by relatives, following social services intervention.
The mother, 31, has recently given birth to her fourth child.
She pleaded guilty to four counts of child cruelty, by neglect, between January and July 2014, when the youngster was six and seven-years-old.
The woman, who cannot be named because of a court order protecting the child, was given a 10 month jail sentence, suspended for 18 months, with supervision.
Sentencing, Judge Michael Stokes QC said: "You left this child alone so you could fulfil your own self-gratification, both sexually and otherwise and you put that before your duty to your daughter - and that's really unforgivable in a mother.
"To leave a seven-year-old child locked in a flat with no means of access or exit; anything could have happened – a fire, an electrical fault or the child falling.
"There's a dozen things that could have happened to the child and that must have passed through your mind when you went to London."
The judge said he was suspending the sentence, "Given the enormous amount of work and investment Social Services have made, it would be counter-productive to send you to prison.
"You now have a tiny child who you are breastfeeding and the last thing the court would want to do is send you to prison in those circumstances."
The charges relate to the defendant leaving the youngster, then aged six, alone in the flat for 20 minutes and then going away overnight.
On two separate weekends, she left her home alone, aged seven.
Mr Gibbs said: "She was barely able to open a window a few inches and the front door was locked with a mortise.
"She conversed with a neighbour through the slightly open window."
When questioned, the mother admitted leaving the child with just "cake and juice" for the entire weekend, whilst she visited her boyfriend.
She said she "felt ashamed."
The pre-sentence report stated the mother "can't be trusted with children.''
She has been the victim of domestic abuse from former partners.
She is still with the boyfriend she neglected her child for, and both are now living with his parents, in a different area, as they supervise the care of the new baby; also being monitored by agencies.
The social service conditions include the defendant and her partner not being left on their own with the baby.
Callinan Clodaghmuire, mitigating, said multi-agencies were intensively involved and the defendant has been undergoing courses, counselling and programmes.
She has monthly access to two of her three other children, including the victim, and is applying to the court regarding seeing her son.
