FITZGERALD/DOYLE

I found a burial site at Ballyknock st mullins cemetery for a mary doyle died 14 feb 1779 and michael doyle died 25 dec 1788, how can you find out what marys maiden name was i am looking for a mary fitzgerald. they had a son daniel who married 1777 to a margaret./mary walsh their son born 16th july 1778 hope some one can help