She was a member of Craobh Móibhí, the youth branch of Conradh na Gaeilge, participating in the group's 1920 production of An naomh ar iarraidh by Douglas Hyde and An tobar naofa by Séarlot Ní Dhunnlainge for the oireachtas drama competition.
Ní Mhuiríosa died in St Vincent's Hospital, Dublin on 27 August 1982, and is buried in Glasnevin Cemetery.
She edited Imtheacht an dá nónbhar agus tóraigheacht Taise Taoibhghile (1954) and Comhairle Mhic Lámha (1955).
Her essay, Gaeil agus Breatnaigh anallód, on the history of Wales won a prize at the 1972 oireachtas competition and was later published as a pamphlet in 1974.
She published a handbook of Irish literary history in Welsh, Traddodiad Llenyddol Iwerddon, with J. E. Caerwyn Williams.
She was a member of numerous literary organisation, and was an acquaintance of other contemporary leading Irish language authors including Máirtín Ó Direáin.