LOWELL - Mary D. (McDermott) Fallon, 73, a lifelong resident of Lowell who was a communicant of Sacred Heart Church, died Thursday, July 11, at her home. She was the wife of James Fallon, who died in 2000.She was born in Lowell on Nov. 28, 1928, a daughter of the late John and Mary (Fitzsimmons) McDermott, and was educated in the Lowell public schools.She is survived by a daughter, Debra Pierzynski and her husband, Joseph, of Lowell; four sons, Michael P. Fallon of Cocoa, Fla., Gary J. Fallon of Newburyport, Kevin J. Fallon of Haverhill, and Edward D. Fallon of Lowell; a brother, John McDermott and his wife, Martha, of Lowell; a sister, Geraldine Regan and her husband, Robert, of West Palm, Fla.; six grandchildren; and several nieces and nephews.Mrs. Fallon also was the grandmother of the late Erin M. Fallon, who died in 1994.