A Worksop carer took £45,003 from a OAP with Alzheimer's disease - withdrawing 36 cheques over three years, a court heard.
Debbie Newbury, 32, sat expressionless as she was jailed for 15 months by Nottingham's senior judge at the city's crown court.
Gregory Dickinson QC told her: "You committed serious dishonesty by taking advantage of the lady who was paying you to help her.
"That is why an immediate custodial sentence is inevitable and essential for serious criminality of this sort.
"The principle of the sentence is just as important as the length."
The court heard that Newbury took 36 cheques over nearly three years, starting in January 2014. One was used to help her buy a car.
Newbury of Church Mews, Worksop, pleaded guilty to fraud with the offence ending by the end of 2016. Another hearing will decide if any cash can be clawed back.
Phillip Plant, prosecuting, said that Newbury started work as cleaner for the woman and later became her carer, being paid between £200 and £250 weekly.
In 2016 - two years after the fraud began - an order was made to help the OAP "looking after her money." The alarm was raised by bank staff the following year and their concerns were reported to Notts social services.
Newbury put the cheques into three of her bank accounts. Some transactions were made after moving the OAP's cash into a current account. At the time, the victim was in her late 80s.
There was the suggestion that some money was used for "treats and outings" for the victim, said Mr Plant.
He told the court that Newbury admitted fraud shortly before she was due to stand trial.
He said: "There is higher culpability by being in a position of trust. There was clearly vulnerability, the victim had Alzheimer's."
Mr Plant said that Newbury was given a 270-day suspended prison term for stealing jewellery from two homes where she worked as a cleaner in 2010.
Robert Sanford, mitigating, said that the offence ended before the pensioner's bank raised the alarm in 2017.
The cheques were usually around £1,000. One went towards the purchase of a car.
He said that Newbury cares for her father and brother, both of whom are in poor health, and will suffer during a prison term.
Mr Sandford told the judge: "She did not procrastinate and had the courage to enter her plea."
He provided a series of references from other people she has cared for - and who knew about the fraud.
"She is highly thought of by others as she has played a role in caring, notwithstanding they know about this," said Mr Sandford.
He urged the judge to give her a suspended sentence, pointing out that a probation report classed Newbury as posing "a low risk of re-offending and a low risk of harm."
She will serve half the sentence before being freed on licence.
Newbury wore a white t-shirt with the word "Luxe" in glitter on the front. As she was being led from the dock, she quietly said: "Thank you."