My error - I apparently misread your posts and thought that Grieg was her maiden name, not her married name. Re-reading them I see that you were searching for Anne Grieg and that Mary might have been her mother, so I should have caught it. (Usually I try to provide both maiden and married name in my posts to avoid exactly that kind of error.)
I am "familiar" with John Fullerton of Marykirk -- and pretty much every other Fullerton from Lunan up to Aberdeen since a significant majority are related to my family. I haven't shown John, however, to be among them yet. BTW, is Nancy Nicol the recorded name? I believe I've seen her also as Ann which is, of course, a variant.
As an aside, the Fullertons in the inscription I provided came from Menmuir originally, and Mary from Lawrencekirk, moving to St. Cyrus after marriage. I have my family in Dun before 1740 and in Benholm after 1760. There was a lot of movement in the area so I'd keep an open mind on possible locations.
Good luck,
Regards,
Wally