Was she perchance Mary Agnes ?
1891, Douglas, district 15,schedule 93, occupying 3 rooms at 38 Cattle Market Lane

Robert Renney, head, married, 45, mason's labourer, County Down
Catherine, wife, married, 46, Douglas
William, son, single,17, mason's labourer, County Down
Mary A, daughter, single, 5, Douglas
William Kelly, stepson, single 24, mason's labourer, Douglas
Catherine Kelly, step daughter, single, 13, Douglas