I don't think Mammy O' Mine is the same song as Mammy - you can see a copy of the sheet music at The Lester S. Levy Collection of Sheet Music - search for Pinkard as author, there are 4 results, 2 with the music online, one of which is Mammy Mine. (Mammy O'Mine will get you directly to the cover page (I think it's a permanent link) and you can follow the links to the subsequent pages).

Mick