Melanie Cole, 49, attacked William Reilly at his home in Tower Gardens, Tottenham, north London, on 29 December. He died a week later.
The Old Bailey heard Cole, who must serve at least 30 years in prison, "murdered him for money".
Cole, of Culford Road, Islington, was cleared of murdering another man in 2005.
Jurors heard Mr Reilly was found covered in blood sitting on his bed, by his son James.Money stolen
He had suffered head injuries after being beaten with a bottle of Chateauneuf-du-Pape and a bottle of liqueur.
The retired builder, who was registered blind and almost completely deaf, died a week later in hospital after developing pneumonia.Zoe Johnson, prosecuting, said Cole killed Mr Reilly for the money he had in his coat pocket.
The court heard Cole would turn up at the house unannounced and had previously stolen money from Mr Reilly after they met in a local pub.
Cole denied the charge and claimed Mr Reilly was well when she left him.
Judge David Paget told her: "It may be that you will never be released and may die in prison.
"You battered to death a 91-year-old man in his home in order to get money from him for drink or drugs. It may have been only £20.
"What is truly shocking is the brutality of what you did."Melanie Cole was ordered to serve a minimum of 30 years in jail
Cole was acquitted of murder in 2005 after two juries failed to reach verdicts in the case of Robin Williams, 47.
Mr Williams was found in a bath at his home in Tottenham having been hit over the head with a bottle and stabbed.
The jury was not told of the previous case because it would have been prejudicial, the court heard.
Mr Reilly, who was born in Balla, County Mayo, the Republic of Ireland, was part of a large family.
In a statement, his son Sean said Mr Reilly, who was much-loved by his friends and family, had been killed in a "brutal and mindless act".
Mr Reilly said: "He stood for decency and integrity - qualities which Melanie Cole knew nothing about."