Emilia Soria was 22 at the time and a domestic abuse victim when she spotted the bankcard lying on a street in Valencia, ThinkSpain reported Wednesday.
With no money and two infants to care for, Soria used the card at a local supermarket to purchase $261 worth of food and diapers.
Police arrested the young mother when she tried to use the card a second time.
Soria was sentenced to two years and four months in jail, community service and a fine of $1,219.
As a first offense, she would have escaped prison if the sentence had been less than two years, ThinkSpain reported.
It is not clear why her prison sentence was postponed until 2013. An attorney specializing in international criminal law is appealing her case.
She is due to go to prison in two weeks.