Did Isabel "Belle" Skaggs ever exist?

This may be another instance of a Skaggs myth taking on a life of its own. Isabel "Belle" Skaggs was supposed by some to be a daughter of Old Peter, however, there appears to be no evidence to support this.  Nevertheless, Belle Skaggs is in many family trees as Old Peter's daughter and wife of a Joseph Fyffe.
The 1820 census for Floyd County, Kentucky lists Old Peter and his sons Lewis, John and Solomon in separate households.  This is a good place to start because it accounts for Old Peter's nine known children:
Lewis Skaggs in his own household
John Skaggs in his own household
Solomon Skaggs in his own household
Nancy Skaggs in the household of husband Miles Terry

Old Peter's household:
3 males 10-15  Moses, Peter Jr, and Christian
1 male 16-18  Jerry (who cheated on his age, probably for tax reasons)
1 male 45+  Old Peter himself
1 female <10  Rutha
1 female 26-44  Martha, wife of Old Peter

We've discussed before that by 1830 Old Peter had other children in his household, likely from his brother Solomon's family.  Frequently this confuses researchers.  Here, in 1820, we are not confused. Nine children, four in their own households.

That said, let's assume somehow we missed Belle Skaggs in 1820.  Perhaps she was in the outhouse when the census taker arrived.  Supposedly she married a Joseph Fyffe so let's try researching that angle.  Look for a Joseph Fyffe or a Belle Fyffe in later census enumerations.

I can't find anything.  There was a John Fyffe from North Carolina who moved to Lawrence County who had sons John, William and a Joseph who married Martha Skaggs, the daughter of John Skaggs and Polly Woods.  So nothing here.

I'm opening this up to the correspondents.  Is anyone descended from Belle Skaggs?  If so, how?