The killer of an 81-year-old Newry pensioner must serve at least 20 years in prison before being considered for parole.
Maire Rankin was found dead in her house in Newry on Christmas Day in 2008. She had been beaten and sexually assaulted.
Last month, Karen Walsh, a 45-year-old pharmacist from Dublin, was found guilty of Rankin's murder.
Sentencing Walsh, Mr. Justice Hart said she had inflicted a brutal and sustained assault on a frail and vulnerable pensioner.
"She inflicted a further degradation upon Mrs. Rankin by removing her clothing and then sexually molesting her in order to make it look as if an intruder had broken in and attacked Mrs. Rankin after the defendant had left," said Justice Hart.
"This additional degradation represents a very serious aggravating factor in an already grave case."
During the trial it emerged that Walsh worked in Dublin, but often stayed at a house she owned next door to Mrs. Rankin. Walsh, who had called around to visit her 81-year-old neighbor on Christmas Eve, lashed out at her with the crucifix which had been given to Mrs. Rankin as a wedding present.
The judge said Walsh's account of her visit to Mrs. Rankin had been "bizarre" and one which the jury had clearly not accepted.
He said she had offered no explanation and shown no remorse.
Meanwhile, 56-year-old man has been stabbed to death in Derry city. Christopher McGaughey was attacked in the Hollymount Park area of Gobnascale. A 31-year-old man has been arrested on suspicion of murder. A woman was also hurt in the attack but her injuries were not serious.
