Molly Martens has been released from prison in North Carolina just before 2pm on Thursday afternoon.
Her father, 73-year-old Tom Martens, left the Caldwell Correctional Centre in Lenoir - about three hours from Raleigh - just under two hours later.
Both admitted manslaughter of Jason Corbett in a plea agreement last year, after their initial conviction for 2nd degree murder was quashed.
The family of Jason Corbett has said they are "deeply disappointed" by the impending release of Molly and Tom Martens.
The Limerick man was beaten to death in his home in North Carolina in August 2015 by his American wife and her former FBI agent father.
The pair had already served 44 months in jail after being convicted of second-degree murder in 2017 but struck a plea deal for voluntary manslaughter.
Their convictions for second-degree murder were overturned and a re-trial was ordered.
The father and daughter were then jailed for a minimum of seven months and a maximum of 23 months at Davidson County Court in November last year for the manslaughter of Mr Corbett.
Ms Martens was admitted to the North Carolina Correctional Institution for Women in Raleigh, while Tom Martens was admitted to the Piedmont Correctional Institution in Salisbury.
Laws mean they won’t be able to live with each other, and can’t socialise unless given approval by parole boards.
On Thursday morning, Jason Corbett's family, vowed to "tirelessly uphold his honourable legacy and seek justice to preserve his memory."
"After a nine-year battle for justice, we are deeply disappointed by the impending release of Tom and Molly Martens, the individuals responsible for the sensless and brutal murder of Jason, leaving his two children orphaned," they said in a statement.
The family added that "the heinous actions of Tom and Molly Martens not only took Jason's life in a malevolent, cruel and vicious manner but they also set about to tarnish his reputation and use his children in a self serving attempt to evade accountability."
"Molly Martens relentlessly put Jack and Sarah into the centre of her bid to evade justice with a web of lies while refusing to take the stand to give evidence herself."
The family added that despite the gravity of the crime "and the immense loss they inflicted, they will be freed [on Thursday] after serving four years and three months."
"Their lack of remorse for the irreparable harm cause to Jason's children, who they callously orphaned, is a stark reminder to all, of their callous disregard for human life and decency."
Mr Corbetts' family added that while the pair have served their sentence, they "now carry the enduring burden of their actions - forever knowing they extinguished a noble life."
"Their legacy is one of undeniable guilt, exposed to an intelligent public - who when they look at the facts and evidence acknowledge their malevolent deeds on August 2, 2015, without the shield of legal technicalities."
Mr Corbett's daughter, Sarah, began her Leaving Cert exams this week from hospital after being treated for a minor illness.
In a post on Facebook, her aunt Tracey, added that she is receiving the best care in the hospital and thanked the staff in Sarah's school who went "above and beyond to organise her exams at the hospital."