I found an 1856 marriage record in Kilmovee for a James Duffy to a Mary Duffy. Kilmovee is loaded with Duffys so this may be another couple. My own Duffys are also from Kilmovee (Magheraboy) and my great-grandmother was Mary Duffy (1858-1939).
I would search both the Swinford and Kilmovee parish registers to see if you can locate Catherine. Sometimes records are missed in transcription
Date of Marriage:01-Feb-1856
Parish / District:Kilmovee RC parish