Smith, who had owned the cat for 10 years, told Mr Blair Possum had been attacked by a dog a long time ago and had been hopping around as a three-legged cat ever since.
She said she had treated the infected wound with Savlon antiseptic cream in the past.
Smith, 40, appeared in Tauranga District Court yesterday and pleaded guilty to charges of being the owner or person in charge of an animal who failed to ensure the animal received treatment that alleviated any unnecessary pain or distress and a reckless ill-treatment of the animal.
Rachael Adams, prosecuting lawyer for Tauranga SPCA, told Judge Thomas Ingram the photos of Possum's injuries were "distressing, even disgusting" viewing and there needed to be deterrent message sent not just to Smith but to all other animal owners.
"It would have been apparent to anyone that this animal was in critical state and suffering terribly.
"This was not a sudden deterioration but a condition which had developed over months not weeks, and there was no excuse for not seeking veterinary care, and there was always the option of surrendering the cat to Tauranga SPCA if Ms Smith could not afford to do so."
Ms Adams said Tauranga SPCA sought a lifetime disqualification for Smith against owning any other domestic animals as she had "abused" the privilege.
Smith's lawyer David Bates said his client was distressed to find herself in court for the first in her life and accepted the situation was "unacceptable".
But Mr Bates said Smith's offending was the "sin of omission" rather an deliberate attempt to deprive her cat of veterinary care and she did not appreciate how ill the cat was.
It was still eating well and jumping on and off furniture and she was not aware of any broken bones.
Financial constraints were behind her failure to seek veterinary care and "naively" Smith had treated the leg wound with Savlon and antibiotics, he said.
Judge Ingram told Smith he agreed with Mr Bates that this was "a crime of omission" rather than a case of deliberate serious neglect.
"I accept unreservedly that you did not know the full extent of the injuries, however the evidence is clear that your cat had suffered pretty substantial injuries, and you should have taken it to a vet for treatment to prevent further suffering by the poor animal," the judge said.