I could not tell from your message whether you had a copy of the actual death entry for Matty Mulholland, Here is the link. The second record son James is the informant. https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_retur...
I searched the subscription site Roots Ireland for all of Ireland and the earliest Martha Smylie baptismal record was in 1824 in Co. Down. Too late for your Martha All of the Martha Smylie baptismal records listed were from either Down or Antrim.
I also searched under Matilda but the earliest record was in 1868.