On Monday Allison Evans was found not guilty by magistrates in Barnstaple after denying causing unnecessary suffering to five-year-old Tiny.
And the RSPCA was criticised by its own North Devon branch chairman for bringing the prosecution.
The court heard Tiny suffered lesions across her body caused by a flea bite allergy and a condition which gives her an urge to scratch.
Miss Evans, 36, of Prospect Place, Weare Giffard, told the court she had no knowledge of the cat's medical history when she adopted it.
She said she asked for help from the RSPCA but it never materialised. Eventually she gave up and returned the ginger cat to the charity.
Speaking after the case she said: "I am in shock. I have always supported the RSPCA but won't now. I was completely stunned to have charges brought against me."
Miss Evans said she was asked by the RSPCA to adopt Tiny, who had been in care for three years and might be put down.
She said she was assured the cat had no medical history.
Some time later she noticed Tiny had some bald patches and asked a vet, who was visiting to look at another of her pets, a sick parrot, to have a look at her. He thought the cat had flea allergy dermatitis and advised her to treat her house and the cat with flea spray.
She said it was impossible to spray the whole house as everything was in boxes following a house fire.
She sprayed the downstairs area, treated Tiny and tried to contain her there to prevent her picking up any fleas elsewhere but it was not working.
Miss Evans said she asked the RSPCA for help but it never came and she felt completely let down by the charity.
She told magistrates: "The last thing I wanted to do was take her back to the cattery. I didn't want her put down.
"It was heartbreaking but I didn't know what else to do. She needed instant help and they were in a position to help her. I am really sad the cat suffered."
Prosecutor, Will Rose, said: "As soon as the condition developed it should have been taken to the vet. It got worse and once it was back in RSPCA care, Tiny improved 70% in a very short space of time.
"Whether the medical information was passed to her or not, the buck stops with her and not once did she take the cat to a professional for an examination."
Miss Evans insisted: "Maybe I made incorrect decisions but I would never have knowingly let the cat suffer."
Nigel Wraigh, defending, said: "It is the neglect of the RSPCA which has, to a considerable extent, caused the suffering and it has then taken criminal proceedings against Miss Evans."
Philip Clamp, chairman of the North Devon branch of the RSPCA, said the trial was unjust and a waste of funds.
He said: "I was always told the RSPCA wouldn't bring a case against anyone unless it was cast iron and I think this is totally unjust. Allison is undoubtedly an animal lover.
"She was let down by us. She voluntarily returned the cat to the RSPCA. We didn't raid her house. She asked for help and we failed her."
Peter Groves, chairman of the magistrates, said he hoped the RSPCA would now review its compliance procedures.
Tiny has since been re-homed and is now called Poppy.
http://www.thisisnorthdevon.co.uk/RSPCA-case-unjust-waste-money-says-branch/story-13428115-detail/story.html
