After her education, she became a midwife and joined the national maternity hospital Holles street after her involvement in the 1916 Easter Rising.

In 1906 she joined Inghinidhe na hÉireann alongside lifelong friend - and most likely lover and romantic partner - Julia Grenan.

They were sent around the bullet-torn streets of Dublin during the week with despatches, food and ammunition hidden in their long skirts to stations at Boland's Mill, Powers' Distillery, Jacobs' Factory, St. Stephen's Green and the Four Courts.

Women and wounded were evacuated from the GPO on the Friday of Easter Week, but O'Farrell, Grenan and Winifred Carney stayed behind with the remainder of the troops, who retreated to a nearby house in Moore Street.

At 12.45 pm she was handed a Red Cross insignia and a white flag and asked to deliver the surrender to the British military.

She was taken to Brigadier General William Lowe who sent her back to Pearse at number 16 Moore Street with a demand for unconditional surrender.

[6][7][8] Accompanied by a priest and three soldiers, O'Farrell brought the order to surrender, signed by Pearse, to the Volunteer and Citizen Army units at the Four Courts, the College of Surgeons, Boland's Mill and Jacob's factory.

[2] O'Farrell spent the rest of life working as a midwife and nurse in the National Maternity Hospital, Dublin.

[10] Elizabeth died on 25 June 1957[11] while on holiday in Fatima House in Bray, County Wicklow, and she is buried in the Glasnevin Cemetery next to Julia Grenan in the republican plot.

Similarly, their comrades in the 1916 Rising, Kathleen Lynn and Madeleine ffrench-Mullen, are also considered to be another "unstated" couple, as were Margaret Skinnider and Nora O'Keeffe,[4][13][14][15][16][17][18][19] all of whom were featured, along with Eva Gore-Booth and others, in a 2023 TG4 documentary about "the radical queer women at the very heart of the Irish Revolution": Croíthe Radacacha (Radical Hearts).

The series, by RTÉ's Cláracha Gaeilge unit – called Réabhlóid (English: 'Revolution') – aired four episodes with the final one commemorating Nurse O'Farrell.