Donna Smith had twice persuaded her grandmother Barbara Asquith to give her cash earlier the same day.
But she returned later with her partner Alfie Lindop and the pair forced the grandmother to hand over hundreds of pounds and stole her mobile phone.
James Baird, prosecuting, said that Smith, who was living in a tent with her partner Alfie Lindop, visited her grandmother on the Ermine West estate in Lincoln on a regular basis and was given food and cash.
She was also allowed to wash and collect clean clothes.
Mr Baird said: “Although Mrs Asquith was not happy about giving her money she did so.”
Smith was given £50 earlier in the day for a taxi home and then returned and was given a further £60 with Lindop remaining outside during her visits.
Mr Baird said: “That wasn’t the end of the matter because during the early evening both defendants returned. They were banging on Mrs Asquith’s door. Eventually her grandmother opened the door. Again Donna was making demands for money. Mrs Asquith was saying she didn’t have any money.”
The grandmother handed Smith her mobile phone to call for a taxi and although Smith appeared to make a call no taxi arrived.
Smith was asked to leave but then both Smith and Lindop attacked Mrs Asquith. Smith grabbed hold of her and started shaking her and Mrs Asquith was pushed onto her back.
Lindop then pinned her down before the pair stole £700 and made off.
Mrs Asquith sought help from a neighbour and was later taken to hospital for treatment to her injuries to her arms and back.
Mr Baird said that Mrs Asquith had been left shaken and worried by the incident.
Smith, 32, of no fixed address, but originally from Gainsborough, admitted charges of robbery and theft arising out of the incident on September 14, 2015. She was jailed for four years.
Lindop, 33, also of no fixed address but formerly of Trinity Street, Gainsborough, was jailed for three years and four months after he admitted robbery.
He also admitted four charges of shoplifting from Morrisons in Heapham Road, Gainsborough, and from Toys R Us, Argos and Boots in Lincoln. He was given a four month consecutive jail sentence for the thefts.
Recorder Stuart Sprawson told them: “This is so serious that an immediate prison sentence has to be passed upon you.”
David Lee, for Smith, said she was deeply ashamed of what she did and apologised to her grandmother.
He said: “At the time of the offence she was a heavily drug dependant woman.
“She has been addicted since she was 14.
“She was in a relationship in which drugs were playing a very important part.”
Jeremy Janes, for Lindop, said he had been using drugs since his early teens and his life had been blighted by his addiction.
He said: “He is desperately sorry he became involved in this.
“His resolve is to turn his back on class A drugs.”