Pauline Tully received a number of wounds in the attack at her home in Kilnaleck, Co Cavan, at around 2pm.
Mr McAuley, aged 49, was one of the men convicted for the manslaughter of Det Garda Jerry McCabe in June 1996.
On Christmas Eve, gardaí were called to a domestic disturbance at Kilnaleck and found Ms Tully. She was brought to Cavan General Hospital, where surgeons treated her injuries.
Mr McAuley was arrested nearby and detained under Section 4 of the Criminal Justice Act.
However, he had to be brought to hospital later, where he was during all of Christmas Day and most of St Stephen’s Day.
He was due to be discharged last night, where gardaí were waiting to bring him back to the station. He can be held for 24 hours, excluding of breaks and hospital visits.
Detectives were eager to put further questions to him before consulting with the Director of Public Prosecutions as to whether or not there was evidence to warrant charges being brought.
The couple have two children, who are being cared for by relatives.
Meanwhile, a 26-year-old woman is due to appear in court on January 9 in connection with the stabbing of a man on Christmas Day in Drogheda, Co Louth.