I have read your letter and think that I might be able to fill in some gaps. I believe that Mary Malloy who you have mentioned is quite possibly my great aunt?!
My grandmother was Agnes Malloy and she lived in Lurgan, County Armagh. She had a sister called Mary that I know about, Agnes moved to Glasgow around 1916 (or at least thats when she was married) but i dont know what happened to Mary?! Thats about all i know im not sure if your Mary had any other siblings and if there is any connection between the two but please e-mail back if you think we might be getting anywhere!