Three workers at the Old Deanery in Essex, who were caught on camera during an undercover Panorama report, last week admitted assaulting residents.
Gill Lee's mother Joan Maddison, 85, was also shown being insulted and goaded in the 2014 documentary.
Mrs Lee said she had known that "something was wrong".
She said she became suspicious after her mother, who has dementia, appeared to "change overnight" after she was moved to another room in the Braintree home, with different carers.
"Before that she was very happy, she was described as a social butterfly and it was a joy to see her flourish.
"It was almost like an overnight switch in her attitude and becoming very wary of certain people," she said.
The management dismissed her fears, she said, and "no-one was prepared to listen" at the home.
"My sister and I knew something was wrong, and that gut instinct, if you have that feeling, you must follow it through.
"It was a relief to know we weren't going mad and we were vindicated in our continual quest to find answers," she said.
The family has decided to keep former social worker Mrs Maddison in the home because she seems "very happy again" now the workers have been dismissed.
The three carers, Adeshola Adewura, 33, Lorna Clark, 45, and Anita Ray, 47, will be sentenced at Chelmsford Crown Court next month.
They were were charged with assault after detectives saw the programme and began an investigation.
Former owners Anglian Retirement Homes apologised "unreservedly" for the abuse at the time.
The home is now called the New Deanery Care Home and is owned by Sonnet Care Homes, which said it has "invested substantially" in staff training.
The daughter of an elderly woman who was filmed being slapped at a care home has said it was "devastating" to watch secret recordings of the abuse.