She was educated through Irish at Eccles St. Dominican convent before going, in 1957, to University College Dublin to study French and English literature.
After graduation Sheehy studied art history at the École du Louvre from 1961 to 1963 and also worked as an assistant.
Before going back to college, Sheehy also worked for Donald Davies as a woven fabric designer in Enniskerry, County Wicklow.
[3] From 1970 to 1973 Sheehy was both research assistant and co-author of Fr Cyril Barrett SJ.
She was on the committee of the Society of Architectural Historians of Great Britain, the Victorian group of the Oxford Architectural and Historical Society and was a member of the Oxford diocesan advisory committee on the care of churches.