Gardai are able to quiz Lisa Smith over suspected terrorist offences for another 24 hours.
The 38-year-old, from Dundalk, Co Louth, had her detention period extended for another day on Tuesday morning.
She is being held at Kevin Street Garda Station in Dublin following her arrest at Dublin Airport on Sunday.
The jihadi bride returned from Instanbul, Turkey with her two-year-old daughter - both of whom are Irish citizens.
A garda spokesman said: "The detention period of the Irish Citizen (38 year old female) arrested on Sunday 1st December 2019 at Dublin Airport on suspicion of terrorist offences, has been extended a further 24 hours and she remains in Garda custody at a South Dublin Garda Station.
"She is currently being detained under the provisions of Section 30 of the Offences against the State Act, as amended."
The former Defence Forces member converted to Islam in 2011, then quit the Air Corps and in 2015 travelled to Syria, through Tunisia.
It’s understood Smith was married four times and the child’s father was a British jihadi who was killed while fighting for the group.
Smith worked on the Government jet while in the Air Corps and accompanied former president Mary Robinson and Taoiseach Bertie Ahern.
Smith and her daughter were put into a camp for ISIS widows and children on the Syrian border.
She escaped last month following the Turkish invasion before she was picked up and handed over to Turkish officials
She arrived on Sunday on a Turkish Airlines flight and was accompanied by two members of the Army Ranger Wing and officials from the Department of Foreign Affairs.
