There are two Nancy Daniel's being conflated, one who married William Giles and another that married John Greene. I have uploaded census and marriage records relevant to each person that proves this. Here is a summary of their basic info:
Nancy Daniel, wife of William Giles, was born in the year 1785 and passed after 1850. See William and Nancy Giles' 1850 census record which indicates this. Their marriage record indicates they were wed in 1805
Nancy Daniel, wife of John Greene, born in the year 1789 is not found on the 1850 census record for John Greene, which indicates she passed before 1850. Their marriage record indicates they were wed in 1808 and again in 1809.
Nancy Greene (Daniel) was more likely the daughter of Frederick W Daniel and Elizabeth Daniel due to the fact Nancy's brother Denton Daniel was born in 1785, making highly unlikely that William Giles' wife Nancy was also their daughter.
For this reason, I have disconnected the Giles connections to this Nancy Daniel. I believe both of these Nancy's were 1st or 2nd cousins, but this I cannot prove yet and is solely my own conjecture.