What an interesting story! Just last night I was talking with my friend's girlfriend and this very topic came up. Her family is originally from North Carolina and fits many of the characteristics of the Melungeons. When I first met her, I thought she must be at least biracial, probably triracial, but I had no idea what races those were and which ones predominated in her heritage. Turns out, she doesn't know either. Her family has traced back their lineage all the way to mid-1700s North Carolina. They have yet to find a direct ancestor who was not of mixed race. They have searched for an ancestor who was all white or all black, and just cannot find one in 250 years. Most of the time, they can't even tell what races these ancestors were descended from - they just know that they were "mixed" but mixed what is anyone's guess. They theorize that their family is a mix of English, African, and Native American blood, but Melungeon is also a distinct possibility.
Have her do the "tooth & head" test. See my post #78.