Mandy Susan Vickers, aged 31, of Lupton Road, Lowedges, has been locked up for seven-and-a-half years, after admitting the crime spree.
Sheffield Crown Court heard how she robbed a man in his 90s while he waited for a bus in the Manor area of Sheffield in November 2016.
She asked the OAP for some change and when he refused to hand any over, became aggressive and threatened him with a knife.
In May 2017, Vickers burgled a property in the Lowedges area of the city.
She asked the occupant, a woman in her 80s, if she could use her phone and when she was allowed entry, Vickers stole a purse.
The next day, Vickers returned to the same property, forced entry, assaulted the woman and grabbing a box containing a small sum of money.
Detective Inspector Anna Sedgwick, from South Yorkshire Police, said: "This is a great sentence for an individual who targeted elderly, vulnerable members of our community for her own financial gain.
"Burglary and robbery are incredibly distressing experiences and I hope that those affected by Vickers’ crimes are reassured by the jail sentence handed down at court.
"I’m grateful to the investigating officers PC Christopher Moran and DC Dave Ollerenshaw who worked hard to gather evidence to bring this case before the courts and their combined efforts have resulted in this sentence, taking a criminal off our streets and putting them behind bars."