The 43-year-old woman, from the Burntwood area, abused her position as the victim's power of attorney for six years.
She exploited her role to make online payments from the woman's bank account totalling £39,466.40 and used her bank cards to buy items worth £43,488.02.
Power of attorney gives a dedicated person the power to manage someone's bank accounts, bills, benefits and house sales should they be injured, ill or be unable to make their own decisions.
The fraudster, who has not been named, was found guilty of two counts of fraud and sentenced to 30 months in prison at Stafford Crown Court.
Detective Constable Joanne Billings, from Staffordshire Police's adult safeguarding team, said: “She was in a position of trust and she helped herself to the assets she was supposed to be managing.
“Those with power of attorney or deputyship should make decisions that are in the best interest of the person they are assisting. There are very strict rules about what can be given as gifts and claimed as expenses to prevent this sort of behaviour.