Joanne Duke, from Bulwell, befriended the pensioner by talking to him as he sold items outside his flat.
But she revealed her true nature two weeks later by asking to use his toilet but then stealing £250 cash from his living room and threatening him with a knife.
The 45-year-old pleaded guilty to robbery at Nottingham Crown Court after police found her fingerprints inside the flat – disproving her initial claim that she had never been in there.
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Duke – who has a string of convictions including theft, assault, robbery, burglary and criminal damage – met the elderly victim as he sat on his deckchair selling items outside a block of flats in Bulwell last summer.
She spent several minutes talking to him before leaving and saying ‘I’ll pop round and see you at some point’.
That moment arrived a fortnight later when she went to the man’s flat and asked if she could come in for a chat, telling the pensioner her son had recently died.
The elderly man, who lives alone, obliged and she left a while later.
A couple of days later, on July 18, she was back and asked for a glass of water and to use the elderly man’s bathroom.
She then asked the pensioner if he could fetch her a towel and when he returned she was holding an envelope containing £500 of his savings.
He tried to grab the envelop back and Duke then ran into the kitchen and grabbed a cutlery knife from the sink and moved towards man while holding it above her head as if she was about to attack him.
Fearing for his safety, the man retreated and Duke then fled with £250.
Police arrived within minutes and enquiries led to Duke being traced to her home address a short distance away.
She was arrested on suspicion of robbery – an offence she vehemently denied during her police interview.
Duke told officers she had never stepped foot inside the man’s flat, but fingerprint evidence from a glass inside the property and CCTV footage suggested otherwise.
Duke finally admitted her guilt at Nottingham Crown Court on January 4 and was jailed.
Investigating officer PC Conor Bullivant said he was pleased with the seven-year prison term handed to Duke.
He said: “This was an incredibly distressing experience for Duke’s victim and the sentence reflects the seriousness of the offence.
“Duke targeted an elderly man, in his own home, despite the kindness he showed her and I am delighted that she will not be a threat to the public for some time.
"As a result of this incident, the victim has had trouble with trusting people within the community and was put off going for walks which he used to enjoy as part of his daily life.
"He is extremely happy with the verdict received and I am extremely thankful for the bravery that the he showed throughout the investigation."
Detective Sergeant Nick Wood, who oversaw the investigation, added: “We take any robbery extremely seriously but particularly one where a weapon is used to threaten a victim.
“The sentence Duke has received shows that behaviour like this will not be tolerated in Nottinghamshire.
"I am pleased with the sentence which was the result of a great effort by PC Bullivant and some brilliant team work, as well as a quick and efficient arrest by the initial attending officers.”