Jo-Ann Quinn stopped family members visiting her sick, elderly mother that she left to "fester" on a couch, her niece says.
Trena Quinn said she wanted her aunt to go to jail for severely neglecting her grandmother.
She was relieved when the judge found Jo-Ann Quinn, 51, guilty of failing to provide the necessaries of life to Maureen Quinn.
Medical staff called to her Napier house on November 15, 2011, found that the fibres of the blanket covering her had grown into a leg ulcer that was infested with maggots.
Outside of the Napier District Court, Trena Quinn claimed her aunt stopped family members from seeing Maureen.
"If you rang and asked if Nana was okay or if she needed anything, she'd say 'no, she's okay. She's asleep. You can't talk to her'," she said.
"She had the windows nailed shut.
"If you'd go there and bang the doors she'd call the police on you. I had them rung on me. She was pretty scary." It was a relief when her grandmother was taken to hospital and cleaned up.
"She looked the best she had in years. Jo-Ann just left her there to fester basically."
Trena Quinn said Jo-Ann Quinn was a recluse and her mother and father used to do the shopping for her before they became ill.
"She refused to work and couldn't get the benefit so Nana and Grandad paid for everything for her out of their pension," she said.
Trena Quinn said her grandmother "was a legend" who doted on all her grandchildren, whom she helped raise.
"I remember being a 7-year-old folding cloth nappies with her and making formula milk," she said.
She admitted her grandmother was a private person but there were ways and means around that.
Judge Jonathan Down said Jo-Ann Quinn neglected her legal duty by letting her mother fall into a severely dehydrated and malnourished state.
Maureen Quinn had not moved from the couch for at least three years, the court was told.
Medical staff called to the house on November 15, 2011, found that the fibres of the blanket covering her had grown into a leg ulcer infested with maggots. Jo-Anne Quinn said it was the first time she had noticed the maggots.
Her mother's face was stained blue from the couch, and her left toenails were so long they had become embedded in her right leg.
She died 36 days later of pneumonia.
Quinn rang a doctor only after her sister in Australia raised concerns about how much pain their mother was in.
Judge Down said it was "too little too late" as her mother's deterioration must have been obvious for some time.
The "compelling medical evidence" meant he had reached an "inevitable" conclusion that Maureen Quinn's life was in "imminent" danger under her daughter's care.
Judge Down said the warmth and comfort of touch must have been missing from Maureen Quinn's life. When Detective Toni Leppien touched her hand she said she said: "Your hand is so warm. I cannot remember the last time someone touched me."
Judge Down said Maureen Quinn couldn't believe she'd ended up in such a poor state as she'd had eight children.
Her youngest daughter stormed in to the courthouse before the verdict and slapped Jo-Ann Quinn in the face.
The woman fled and has since been trespassed from the court.
Jo-Ann Quinn was remanded on bail to be sentenced on May 16.