Tegan Doidge broke into the £300,000 home where she grew up and stole £7,500 cash from her mum and dad's bedroom.
Her father, John Doidge, 50, who runs his own business contracting company, called police after realising the money was missing.
The teenager was found with cannabis and just £150 left of the money. The extraordinary story of how a middle class girl came to end up stealing from her own family was told at Exeter Crown Court.
It heard that Doidge had left home and was sleeping rough in picturesque Ottery St Mary, Devon.
On the night of her crime, Greg Richardson, prosecuting, said Doidge had been ordered out of her parents' home but returned and was seen by a neighbour breaking in through a cat flap in November last year.
She found £7,500 cash in a drawer in her parents' bedroom and took it. The money was savings to buy a truck and trailer for her mother's horses.
Doidge, who admitted burglary, was originally given a community order but was re sentenced after failing to carry out 120 hours' unpaid work.
She was sentenced to two months in a young offenders' institution as her mother Melanie, 42, sobbed in the public gallery.
Mother-of-five Mrs Doidge, an NHS carer for the elderly, said: "Tegan has difficulty understanding times and situations. It is all a cry for help.
"I will stick with my family, whatever they have done.
"Jail will be a shock for Tegan and that is maybe what she needs."
Judge Ambrose told Doidge a custodial sentence was the only option due to her 'chaotic lifestyle'. He said:
This is a short sharp shock to bring home to you the effect of not complying with this order but without crushing you or introducing you to a criminal lifestyle.
"You have proved singularly incapable of fulfilling promises and the explanation for this is your chaotic lifestyle, living on friends' sofas.
"It is a situation you have brought fairly and squarely upon yourself."