Thomasina Bennett, from Belper, had Alzheimer's Disease and was staying at Milford House Care Home in April 2012.
Milford House Partnership had denied two health and safety at work charges, but were convicted of one relating to personal activity monitor alarms (PAM).
Derby Crown Court heard the monitors were "systematically unsafe".
Gerald Hudson, 72, from Ambergate, trading as Milford House Partnership, was found not guilty of the other charge, which related to the fastening of the wardrobe onto the wall.
Another hearing is taking place on Thursday which will seek to determine a sentencing date.
Mrs Bennett's daughter Margaret Calladine, said the last four years have been "an emotional rollercoaster".
"It seemed, on paper and from the people we spoke to, to be a place that we felt that she should have been safe in," Mrs Calladine said.
"I hope they've learned their lessons, and that legislation will be tightened up on how care homes have to care for these vulnerable people."
The court was told the monitors were supposed to alert staff if residents got up in the night - but Mrs Bennett's alarm had not gone off before she was found.
The PAMs were used in multiple rooms, but could only show one alarm at a time.  In other instances, they would appear to be working when they were not.
A Milford House Partnership spokesman said the firm was "devastated" by Mrs Bennett's death and that their thoughts "continue to be with her family".
"No legislation or guidance currently exists in relation to the fastening of furniture in care homes or other healthcare settings," the spokesman said.
"However, we will continue to campaign for the Health and Safety Executive to review this and release guidance to the care industry to prevent the re-occurrence of such a tragedy."
The spokesman added the company told the jury the monitors were an "additional aid" and did not replace checks carried out on residents every two hours.
Amber Valley Borough Council, who investigated the care home, hoped the verdict will have "far-reaching consequences" for improved health and safety standards in care homes across the UK.
A care home firm has been convicted of a health and safety charge after an 80-year-old woman died when a wardrobe fell on top of her.