Her father was a Royal Irish Constable while her mother ran a drapery shop in the town.

[2] Count Plunkett was visiting the town of Sligo in 1917 following his victory as Sinn Féin MP in the North Roscommon by-election and stayed with the Mullane family on Grattan Street.

Countess Plunkett told O'Mullane about Cumann na mBan and how they were recruiting and needed a branch in Sligo.

O'Mullane was responsible for maintaining communications with units in Counties Down, Derry, Kildare, Louth, Meath and Westmeath.

[14][15] After the war, O'Mullane was a member of the Friends of Soviet Russia and took part in various conferences between workers.