The SPCA said the woman told the inspector she fed, walked, bathed and brushed the dog but could not afford a trip to the vet.
"She said she had previously mentioned to the owner that the dog needed to see a vet but nothing had happened."
The SPCA inspector removed the dog from the property and took it to the Wellington SPCA veterinary centre.
"After only 48 hours the dog's condition had improved and the scratching had ceased. Within four weeks its skin showed great improvement with the hair re-growing and only a few small areas of inflammation present."
The SPCA said it charged Deborah Hohua under the Animal Welfare Act 1999 for ill-treating the animal.
The animal welfare society said the woman was found guilty at a hearing in Wellington held on Tuesday.
"She was subsequently ordered to pay $500 reparation to the SPCA and $100 towards legal costs," the SPCA said.
"This case is a reminder that people who take on the care of others' animals also have a legal responsibility not to allow an animal to suffer any unnecessary or unreasonable pain or distress," Wellington SPCA chief executive Steve Glassey said.
"In this particular case, nothing was done to alleviate the pain and distress being suffered by the dog for ten weeks," Mr Glassey said.
"If the defendant had sought veterinary attention for the dog or contacted the SPCA straight away, the result would have been significantly different."
The SPCA said Wellington criminal barrister lawyer Elizabeth Hall donated her time to support the SPCA's inspectorate, and led the prosecution.
