Gifford experienced the living conditions of the landless rural poor while lodging in labourers' cottages during this time. As a result, she became a supporter of the campaigns of the land agitator and nationalist MP Laurence Ginnell.
She was also influenced by her sisters' nationalism and feminism. With them, she became involved with the Irish Women's Franchise League, and got to know Constance Markievicz. She got parts in stage plays, including Eleanor's enterprise by George Birmingham in the Gaiety Theatre, a play produced by the countess's husband, Count Casimir Markievicz.[1][4]
During the 1913 Dublin lock-out she assisted James Larkin enter the Imperial Hotel, on 31 August to address the crowd. He entered in disguise, that of an elderly and infirm clergyman. Gifford posed as his niece. She spoke to the hotel staff to prevent Larkin's strong Liverpool accent giving away his identify. This was the speech which precipitated the "Bloody Sunday" police baton charge. Gifford went on to be a founding member of the Irish Citizen Army (ICA). This group was attractive to many women due to the feminist beliefs of James Connolly.
She gave lessons on camp cookery in Liberty Hall and found jobs for recruits coming in from abroad. As a result of this work she, very fatefully, introduced Michael Collins to her future brother-in-law Joseph Plunkett who went on to serve together in the 1916 Easter Rising; Collins was Plunkett's aide-de-camp.[1][5]
Gifford was the only one of her sisters to actively participate in the rising itself. She was with the ICA's St Stephen's Green contingent alongside Countess Markievicz. Throughout the week she supervised the garrison's provisions in the College of Surgeons' building, commandeering food from shops and bread vans, and by courier from other garrisons. She also ensured the delivery of provisions to troops both in the college with her and in outlying posts. Gifford was one of the women arrested at the surrender and jailed in Kilmainham Gaol. At the same time, in the same prison her sister Grace married Joseph Plunkett hours before his death. Only twelve women were detained after the main release women prisoners on 8 May 1916. Gifford was one of those transferred to Mountjoy Prison until her release on 4 June 1916.[1] Afterwards she continued to be as involved in the campaigns.[6][5][7][4]
After her time in prison, Gifford travelled through England to the US where she and other women veterans of Easter week lectured throughout America. While there she married Joseph Donnelly, of Omagh, County Tyrone in 1918. In 1921 she and their year-old daughter Maeve left him to return to Ireland.[1][8]