Mary Martin of Gallows Street might be a sister in law, maybe.
Here is
May 6, 1900
a death of a Mary Louisa Martin, 18, of Gallows Street, daughter of a seed merchant, with mother Mary Ann Martin, also of Gallows St as informant.
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1900/05763/4628442.pdf---------
Mary Louisa Martin's birth, 15 September 1881, daughter of James Martin, a grain merchant of Meeting Street, Dromore, and Mary Anne Martin, formerly Derry.
https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_returns/births_1881/02819/2034176.pdf------
Still looking for James Martin and Mary Anne Derry's marriage to see who James' father is.