Been a while, but I've been sleuthing around and I might have found some clues
On her marriage certificate in Cork 1878, the residency for her father Timothy is Roman Street.
Now I looked through the death records and I found a Mary McCarthy who died in 11 Roman Street in 1892. She was a dressmaker and was 64 years old born c. 1827/1828
This could be Timothy's wife and Bridget's mother because I looked around and there is a marriage record in 1855 in Glenflesk Kerry to a Timothy McCarthy and Mary Horgan. The witness is listed as Denis Horgan, which is likely Mary's father because there is a Mary Horgan born in 1827 to Denis Horgan and Gobnet Reen in Glenflesk.
Now what links the Horgans to Bridget McCarthy and William Fitzpatrick in 1878 is that there is a witness to their eldest daughter Ellen's baptism in 1879 Cork, her name is Kate Horgan.
Get this, there is a baptism of a Catherine Horgan in 1845 to Denis Horgan and Gobnet Reen, this could be the witness.
Kate is more than likely Mary's sister, which makes her Ellen's great aunt.
Trouble is, I can't find a baptism for a Bridget McCarthy born to a Timothy McCarthy and a Mary Horgan, so this all could be for nothing.
Any thoughts?