Sister Ancilla Domini was born Kathleen O’Reilly in Bruskey, Co. Cavan in 1914. She received her early education in Cavan and joined the Medical Missionaries of Mary in 1951.

Her first assignments were in catering and hospitality in MMM houses in Ireland, beginning with three years in Drogheda. She next spent twelve years in catering in Rosemount, the MMM house of studies in Dublin. She was noted for her kindness to the students. No matter what time they arrived back from lectures, she gave them a warm welcome and had a hot meal ready. Following this she worked for nineteen years in the kitchen in Drogheda.

In 1987 she began her ministry as the sacristan in Our Lady of Lourdes Hospital, which she did with love and devotion for eighteen years.

Sister Ancilla retired in the MMM Motherhouse, Beechgrove in 2002. She transferred to Áras Mhuire in 2005. Her life revolved around the Mass and she spent many hours praying in the oratory.

She was the oldest member of the congregation when she died on 6 December 2012.