Meanwhile, it has also been revealed that prosecutors feared Karen Walsh was planning to evade justice by getting plastic surgery to alter her appearance and leave the country.
This follows a request for facial surgery and claims by two female prisoners that she enquired about how to get a fake passport.
Ms Walsh's legal team denied that their client was planing to flee and disputed the significance of the cosmetic surgeon's intervention, saying Walsh had been getting botox for 12 years.
Mrs Rankin's daughter Mairead said her mum was a victim of her own kindness, and would never have turned someone away from her door.
"My mother had only met Karen Walsh on three occasions, and on each occasion she called late at night, with drink, and was hard to get rid of.
"She told my sister Brenda and brother Diarmuid about Walsh calling with drink, and that she couldn't get rid of her.
"They wanted to tell her that my mother wasn't able for it, but my mother said, 'No, you can't be rude to your neighbours. She was polite and hospitable, but she viewed Karen Walsh as a nuisance," said Mairead.
The Rankins believe the row that sealed their mum's fate began when Maire possibly told Walsh that she should be with her family at Christmas.
"My mother would not have tolerated drunks in her house. On Christmas Eve she (Walsh) drank almost a full litre bottle of vodka," Mairead added.
"Mum was religious, and she hadn't been able to go to mass, so she was watching midnight mass when Karen Walsh called with the neat vodka.
"We can only assume that our mother said that on Christmas Eve she should have been with her little boy and her husband, and that she had reacted to this with anger and violence."
Mairead said the family were horrified to learn of their mum's murder on Christmas Day -- but the news of the sexual assault with a crucifix almost sent them over the edge.
"We were so shocked you can't begin to understand," said Mairead. "When the police told us about the sexual assault we just could not believe it, we wanted to protect our mother's dignity."
Mairead added that it was "our assumption was that it was a man that attacked our mother", adding: "And then on the 31st we were all in my sister Brenda's house when we got a call that somebody was being charged in Newry at 2pm. It was about noon at this time.
"We all went to the court, and were then told it was a woman. I just could not believe it. It was the first time I saw Karen Walsh, not five feet away. It was surreal."
On the guilty verdict, Mairead said: "It was unanimous, and the foreman was very emphatic when he said it. My heart was thumping. I struggled not to cry. I wanted to maintain a dignity for my mother. We had known the truth all along. And she didn't flinch. We had been gagged for three years, and it was great to see justice done," she added.
"Hearing the judge say 'Take her down' was just such a relief. Karen Walsh didn't even react. She just gave her mantra of 'I'm totally innocent' as she was led to Highgrove. She's there now and we are happy," she added.
Describing Karen Walsh, Mairead said:"She is pure evil, and during the trial we wondered did other people see her the way we did. There was no motive, nothing. She denies having anything to do with it."
"Karen Walsh robbed mummy of her last years, and he two sisters aged 80 and 82 will never get over it.
"They have lived with this nightmare," said Mairead.
"There was no reason to kill our mammy. You could not go into Karen Walsh's mind.
"She is a very evil and disturbed person."
See pages 22-23