"We didn't want him to lose his job over it as he had already lost a fair bit of respect," she said. "But it's a little bit annoying, I suppose, that absolutely nothing has come of it. The fact that they say that it didn't meet the threshold for criminal charges, well what does meet the threshold?"
Zeta still ran around as if nothing had happened, she said, although she had noticed some small changes.
"He's still the same old friendly old thing ... he breathes a bit funny now and he snores a lot more than he used to."
The police officer involved was "very remorseful", she said, and had offered to pay any future vet's bills related to the injury.
"At the end of the day he's a good guy ..."
RNZSPCA chief executive Rick Odom said the matter appeared to have been investigated thoroughly.
"If the SPCA was investigating this we would look at all of the evidence ... and then in every case you make a judgment call as to whether or not it is in the public interest to take a prosecution.
"I would assume the police have done the same thing."
The founder of animal welfare group Helping You Helping Animals, Carolyn Press McKenzie, said there should have been some consequences for the officer's actions.
"I think it was a reckless and a cruel thing to do, and had it been a person it would have been a very different outcome."
It also highlighted the need for all dog owners to ensure their pets were properly fenced into properties.
A police spokeswoman said the officer was still working and because the matter was now the subject of an employment inquiry there would be no further comment.
According to the law
Under the Animal Welfare Amendment Act 2010, it is an offence to wilfully or recklessly ill-treat an animal involving prolonged pain and suffering and the need for veterinary treatment.
If an offender is charged under the act they could be liable for reparations - anything from a small fine to jail time.
All charging decisions made by police are made in accordance with the Solicitor-General's guidelines.
They state that prosecutions are initiated or continued only where the prosecutor is satisfied that the test for prosecution is met.
The test for prosecution examines evidence, public interest and likelihood of successful prosecution to determine viability.