I know this is 12 years late but I just found your post. You are talking about my great aunt Mary. I remember her and I was frequently in the Warren Street house. The Dennisons were her sister's family. John Dennison was her brother in law. She was not a nun, but she was Catholic. She died in 1971. She and her siblings are all in my family tree on Ancestry.
You can contact me through Ancestry messages.