michael, I'm sure your "Song Theft Police" comment was tongue-in-cheek. I don't think you can "steal" a traditional song by writing and claiming copyright to a new arrangement or version of it. Tons of folk and c/w and jazz artists do that. [Unfortunately, many folks may see the © on your sheet music or recording and be deterred from using even the public-domain versions.] *G*

So if Nancy's song is a new version or arrangement of a trad song, she is, of course, entitled to songwriting royalties if someone else uses her version. Folks can still work from the older versions, though, without owing royalties.