Lynch (51) is serving a life sentence for the murder of bread delivery man David Darcy who she mistakenly believed was involved in the murder of a Continuity IRA member.
Lynch admitted last April to shooting Mr Darcy dead outside his home in Ballyfermot in November 2011.
The court heard she told gardai she was an IRA volunteer and would die that way.
Her father, Joe Lynch, told the Herald that his daughter was subjected to an "unprovoked attack" by an inmate who had recently been transferred from Dublin's Dochas Centre.
"She was attacked in the kitchen. She was getting milk from the fridge and this inmate came up and struck her with a blunt instrument," he said.
He added that he believed the attack was an attempt by the inmate to get sent back to Dublin.
"My daughter gets on with all the other inmates. She was a drug councillor and is still a drug councillor," said Mr Lynch.
"She needed four staples underneath her ear. My daughter is a strong girl, this kind of thing doesn't bother her.
"I was with her yesterday and she was in great form, laughing and joking. She shrugged it off."
During Lynch's trial, Det Insp Colm O'Malley told the Special Criminal Court that victim Mr Darcy was a "wholly innocent" father of two who was simply going about his daily life.
Mr Darcy's father, Henry, said his son had been planning to wed Amanda Haverty, his partner of 22 years and the mother of their two children.