Nancy may well have been an Indian. Unfortunately, she would have been too early for most of the records. The records are better for those Indians that lived on Indian lands up til the removals.
The Borens were in the right area in Tennessee and if from Rowan County North Carolina other Cherokee families have come from this area. Many of the early settlers, like the ones that moved with Bowles and others who moved around the same time, collected payments for the lands the ceded in the treaties of 1817-1819, in 1830.
I have not found the Borens listed in this list. If Nancy had an Indian name she could have used that. But I suspect she cannot be found there.
I suspect that if this heritage exists there will be no way to confirm this heritage. My great grandmother always spoke of the Indian ancestry, but I was too young to know what the right questions were to ask.