Sister Muredach was born Sheila Hallinan in Knockroe, Castleconnor, Co. Mayo in 1927. One of a family of eleven, she received her early education in Sligo and trained in shorthand and typing in Ballina, Co. Mayo. She worked as a clerk-typist for Mayo Vocational Education Committee for several years and was the personal secretary to the principal. She joined the Medical Missionaries of Mary in 1950.

Sister Muredach worked in Drogheda in the maternity and outpatients’ offices and after profession in 1953, she was assigned to Nigeria. She was the secretary in Ogoja for three years.

She returned to Ireland in 1956 to do fundraising through the Sweepstake. She did this for twenty-six dedicated years. From 1983 to 2009 she was the sacristan in the MMM Motherhouse and did this with great reverence. This was in addition to other duties in the convent. She typed requests for prayers, remembering monthly anniversaries.

Muredach also enjoyed music, reading, and riding her bicycle. She often cycled down the town to Adoration in the parish church. She was a woman of great prayer and spent hours in front of the tabernacle.

In 2009 she moved to Áras Mhuire. Sister Muredach died on 13 December 2013.