There's a burial of a Margaret Cooile at Rushen on 28 Dec 1837 that gives the age as 63 so if this is your Margaret you're looking for a c1774 birth. There are two baptisms of a Margaret Crow in Lezayre that year: 16 Feb 1774 to John Crow & Isabel Gill and 18 Sep 1774 to Ewan Crow & Isabel Vondy.