Karen Walsh has been jailed for a minimum of 20 years for murdering her next-door neighbour Maire Rankin.
Walsh, 45, showed no emotion as Mr Justice Hart sentenced her at Belfast Crown Court.
The judge described the attack as sustained and brutal on an elderly, defenceless and frail woman.
He said Walsh had shown no remorse and her account of events on the night Mrs Rankin was murdered were bizarre in the extreme.
Mrs Rankin was found dead at her Newry home on Christmas Day 2008. She had been beaten and sexually assaulted.
The marks of the crown of thorns from a family crucifix used to beat her were found on her chin.
The judge said: "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.
"This additional degradation represents a very serious aggravating factor in an already grave case."
Walsh, who is originally from Galway, worked in Dublin, but owned a house next door to Mrs Rankin in Newry in 2008.
