Emily's Sister

     I seriously have no business working on my genealogy at night when I am tired and should be sleeping.  Maybe I should dream about these ancestors so I can wake up refreshed and ready to resume sleuthing.  I also need to be more careful when reading records.
     My 2nd great-grandmother, Teresa was baptized in November of 1875.  I have three copies of this sacramental record.  Why three when one should be sufficient?  Well, I had a photocopy of the baptismal certificate that my grandmother's cousin sent me.  It had the name Emily Sheldon as one of the sponsors. That was Teresa's mother's name so I contacted the church myself for another copy.  The second copy had no sponsors listed.  I had put genealogy on hold for awhile then when I looked at these certificates I needed to find out who the sponsors really were.
     Teresa's parents were Patrick Devine and Emily Sheldon.  When I received baptismal information for the third time, it was not a certificate, it was a photocopy from the book with all the baptismal entries.
     The other day I took another look at Teresa's baptismal record while searching records for her mother, Emily.  How did I not notice this?  How could I have put the wrong name on my tree?
     The photocopy of the entry from the baptismal book is most accurate because the church just photocopied that page rather than filling out an actual certificate.  Teresa's godparents were Andrew Carswell and Mary Devine.  I listed Mary as a sister to Emily on my tree because I had gotten used to referring to Emily as Emily Devine and not Emily Sheldon.
     So I guess Mary was Patrick's sister or maybe his sister-in-law.  Patrick's brother, John was married to Mary Jane Corby.  Were they married at the time of Teresa's baptism?  Is Mary Jane Corby the Mary Devine who appears on the baptismal certificate?  I checked my tree again and saw that Mary Jane Corby didn't marry John until 1887.  So maybe the Mary on this certificate was Patrick's sister.
     Is Mary another mystery lady?