Thank you for your help! Stephen Brett (my grandfather)did not have a sister Mary. His parents were John Brett and Ellen Cody. The 2 sisters that may have been nuns were Margaret and Ellen Brett. That Mary Brett may be a cousin. However, my great grandmother was Mary Comerford born in 1830's. She was the mother of Maggie O'Connell Stephen's wife. Both families came from Mullinahone.
The Mary Comerford you found may be the cousin of my grandmother. Maggie was born in 1871. I do not know the parents of Mary Comerford (Maggie's mother) but I should investigate George because that could be a brother. This was great help because I could never find anything on Mary Comerford when I searched. Maggie's (Margaret) father was Patrick O'Connell. Thanks so much I'm going to look at the websites.