"They got their dream home with the help of my money and now I can go to hell – that's how I see it," she said.
It is not an unusual situation. Age Concern, which is running an awareness campaign this week, says family members are responsible for three-quarters of elder abuse cases.
"You read about it and hear about it," the woman said. "And it does happen. But the saddest part is you don't expect your own son to do it to you, or let his partner do it to you. That's the gut-wrenching part of it."
The woman's son denied any mistreatment, telling other family members that she was lying and unstable.
An outgoing person, she said she became "quite sick" as a result of the abuse.
Her sister, a social worker, eventually intervened when she saw how the woman had deteriorated. She referred her to Age Concern.
A lawyer helped her get a protection order against her son's partner, which forbids them from coming on to her property. And she has been advised that, as a part-owner, she can force the sale of their house.
"I'm strong enough now to stand up to it," she said. "I'm not frightened anymore."
The woman has also changed her enduring power of attorney from her son to her sister.
"If I can't trust him in life, how can I trust him in death?"
Age Concern has been highlighting elder abuse in New Zealand this week in a bid to let abused people know how they can get help.
Chief executive Stephanie Clare said shame or stigma often prevented people from reporting abuse within their family.
"This is one of the reasons it stays hidden. Many older people feel ashamed their own flesh and blood are treating them badly, so they won't talk about it."
HIDDEN CLUES
How do you reach elder abuse victims when their abusers often control their lives?
The Government-run Office for Seniors confronted this problem in a campaign which wrapped up last week.
Elderly people in abusive relationships could be closely watched by their abusers, be kept at home, have their calls screened, and their outings limited.
But the Office for Seniors found a way to sneak into their homes unnoticed - through a crossword puzzle.
Over the past two weeks, the crosswords have been placed in 20 newspapers around the country, including the Herald.
Each one features one clue, such as "Controlling who an older person can talk to" and "Making an older person's decision for them".
They always have the same answer, "Abuse", and have a note referring them to the elder abuse hotline (0800 EA NOT OK).
The campaign has had some initial success, the Office for Seniors said. In the first week, the number of calls to the hotline rose 36 per cent.
The hotline was launched last year, and had 2100 calls and referrals in its first five months.
ELDER ABUSE
• 2295 cases reported to Age Concern in year to June 2017
• Interventions took place in 1736 cases
• 79 per cent involved psychological abuse, and 54 per cent financial abuse
• Family members made up 76 per cent of alleged abusers