Plymouth magistrates heard that the RSPCA rescued Bonny from owner Kelly Mooney because it had red, itchy skin.
Mother-of-three Miss Mooney told the court that she loved the seven-year-old dog but had become overwhelmed by family and financial problems.
But she admitted causing unnecessary suffering to the cross-bred terrier by failing to get her treated by a vet between July and August last year.
Mooney, aged 31, was given a conditional discharge for two years but ordered to pay £250 of the RSPCA's costs. She was also banned from keeping a dog for three years and ordered to sign Bonny over to the care of the charity.
The court heard that the dog had made a full recovery and was now ready to be re-homed.
Presiding magistrate John Matthews told Mooney: "Elements of this case are desperately sad but you clearly neglected care of the dog and suffering has resulted. Clearly in these circumstances the dog needs to be rehoused."
John Wyatt, prosecuting for the RSPCA, said: "An inspector attended at her house last August and found the dog to be in a poor condition, and suffering from skin loss and other problems."
He said that Bonny needed immediate treatment and she was taken to a veterinary hospital. Mr Wyatt added that blood tests found that she had suffered no internal damage and she improved after treatment.
Mr Wyatt said that Miss Mooney told the RSPCA in interview that she had last taken Bonny to the vet in 2006. She declined to sign the dog over to the care of the charity.
Julian Jefferson, for Mooney, said she was extremely distressed and "deeply sorry".
He added: "Her overwhelming feeling towards the dog is love."
But Mr Jefferson added that it would be better if the dog was rehomed.
The court heard that Bonny, who had been with Miss Mooney since she was a puppy, had a longstanding problem.
Mr Jefferson said that she had got the dog treated in the past through the PDSA charity.
But the court heard that Miss Mooney's brother died and she had to cope with the stress and cost of the bereavement, as well as looking after three children as a single mother.
Mr Jefferson said that ironically the RSPCA, which ended up prosecuting her, could have helped with Bonny's treatment.