Her formal education in Dublin extended to weekly Gaelic League classes to learn the Irish language.

[4] She was a founding member of the Young Republican Party, advocating against Partition of Northern Ireland as the Home Rule Crisis increased.

She and her sister helped courier ammunition and arms to hiding places for Erskine Childers and were then rewarded with two rifles.

[6] She was sent back to County Tyrone for their safety and to re-muster the Northern Division of the Irish Volunteers, under orders from Patrick Pearse.

[1] After the attempt failed, she returned to Dublin with her sister, but due to train disruptions walked from Dundalk, and spending a night in a field near Balbriggan only to arrive hours after the leaders of the Easter Rising surrendered.

[2] While in Boston she spoke for hours at Faneuil Hall in order to gain American support and recognition of the Irish Republic.

[7] She furthered her efforts by writing a book titled The Unbroken Tradition, in which she describes the events of the Easter Rising, which was subsequently banned as President Woodrow Wilson entered the United States in World War I and it was labelled "anti-British".

Following the outbreak of the Irish Civil War, she supervised an Anti-Treaty first aid post at Tara Hall.

Cumann na mBan was outlawed by the Free State government and in November 1922 she was arrested and imprisoned in Kilmainham Gaol, with many other members.

[10] She supported forming a new political party, but when a resolution was passed to remain as a united front, she and her group withdrew from the congress.

During the 1930s, she was a statistician in the Irish Transport and General Workers Union (ITGWU) and a telegraph agent during the Second World War, until ill-health forced her retirement.

[1] In 1940 Connolly O'Brien was briefly involved with Córas na Poblachta, an attempt by the IRA to create its own political party.

For whatever reason, Connolly O'Brien did not show much interest in the much more successful organisation of the same concept, Clann na Poblachta, which featured many of Ireland's Republican and left-wing figures amongst its ranks.

[15] Nora Connolly O'Brien died in Meath Hospital, Dublin, on 17 June 1981, ten days after being admitted due to failing health.

More than 200 people gathered at her graveside in Glasnevin on that date, and her life was celebrated in the Church of Our Lady of Good Counsel, Drimnagh.