CrowSister asked for:

Characterful and Individualistic Female Voices in Folk Please.

Could you really say there was anything particularly characterful or individualistic about Peggy Seeger or Jean Ritchie's voices? (Or quite a few of the others mentioned here - come to think of it my own suggestion of Zara wasn't of somebody with a notably out-of-the-ordinary voice, though her performance is a bit unusual in doing unaccompanied ballad style in a TV studio). Their voice quality isn't why we listen to them.