The vet concluded the dog's condition was the result of "inadequate feeding for many days, if not weeks", the SPCA said.
"He also stated that being significantly underweight and suffering from mange would have caused the dog ongoing distress and that any lay person should have realised the dog was underweight and in need of veterinary treatment."
SPCA chief executive Christine Kalin said Olive had struggled financially and found it difficult to provide her dog with medication and food.
"This case sends a clear signal to dog owners that being short of cash is no excuse - you are responsible for providing adequate food, vet treatment and other necessities for your animals," Ms Kalin said.
"If you can't provide for your animals then please seek help from family, friends or community organisations."
Lady will be put up for adoption by the SPCA "as soon as possible", Ms Kalin said.