Amy MacDonnell

According to Dictionary of National Biography, 1901 supplement, Brian MacPhelim O'Neill's wife was a daughter of Brian Carragh Macdonnell, 'captain of Glenconkene' (Cal. State Papers, Ireland, 1509-73, pp. 372-3)

There is no hard evidence whatsoever for her being a "Margaret Vardy", and since all family trees that include "Margaret Vardy" lead to the fictitious "Lady Grace O'Neill", there is no reason to believe she existed either.