My copy of Hew Morrison's transcript of the Parish Register of Durness does show the marriage of Donald MacLeod junr. to Ann Mackay on 12 Jan 1779 (not 1799). Their aliases are shown as noted above. However, the entry recording the baptism of the son, James, on 19 Dec 1779 shows the mother as Ann Dalrymple, but her alias is the same, or almost the same. I think the "marriage" alias is incorrect and her patronymic should be nin Nish mac Ean mhic Dhonil, which I read as a phonetic rendering of daughter of Angus, son of John, son of Donald. Donald's patronymic is given as mac Nish bhain ( son of fair Angus). The minister notes that Donald is commonly called "little Donald Bain'
I think it is a reasonable assumption that Ann MacKay and Ann Dalrymple are the same person. When their son Hugh's baptism is recorded on 1 April 1782, Ann Mackay is shown as the mother but is given an alias of Dalrymple. However, she is given a different patronymic, " nin mac achin mhic dhonil" note that I have separated the names in the patronymic; it is recorded as one word. This one is a bit of a mixture but I read it as daughter of Hector, son of Donald. Perhaps the minister got it wrong?
I hope this helps.
IanB