Marie Staniforth, of Eskdale Green near Ravenglass, Cumbria, was locked up last month after an emaciated lurcher-type animal was discovered in Cleator Moor.
The 32-year-old was found guilty of causing unnecessary suffering to the dog and jailed for 18 weeks.
However, she was released on Friday after a court in Carlisle ruled her sentence had been "disproportionate".
An RSPCA inspector had described the animal as "the skinniest dog he had seen alive".
Hearing the mother-of-four's appeal at the city's crown court, a judge and magistrate said the original sentence did not take into account the effect on her family life.
Staniforth, who had spent 10 days in prison, was given an amended two-week prison term and told she was to be released from custody immediately.
A woman jailed for neglecting a dog found close to death has won an appeal against her sentence.