Found these marriage's.

DUFFY _ DOHERTY
January 14, 1902 at St. Eugene's Cathedral, Derry by the Rev McFeeley Adm. William, eldest son of Neil Duffy, Drung, Quigley's Point to Annie, youngest daughter of the late Daniel Doherty, Kindrum, Fanad, Co. Donegal.


McDERMOTT - DUFFY
August 15, 1905 at St Columb's Catholic Church, Drung by the Rev James O'Kane PP. Edward, eldest son of Edward McDermott D.C. Cillinean, Redcastle, to Cassie, youngest daughter of John Duffy, publican, Carrickmaquigley, Redcastle.

also a few obits;
DUFFEY: February 15, 1884 at her father's residence Tullyally, Redcastle. Lizzie, second daughter of John Duffey, aged 28 years.

DUFFEY: May 10, 1900 at his residence Tullyally, Redcastle, Co. Donegal. James Duffey.

DUFFEY: June 29, 1904 at her residence Carrickmaquigley, Redcastle. Rose, the beloved wife of John Duffey, publican.

Hope this helps!