Peggy doesn't say it was the first time she heard it but I guess it was the worst version, to make her laugh.
Big brother Pete knew Leadbelly so chances are she knew him too and even if she hadn't heard him sing it live, would no doubt have heard a recording of the original.
Back about 40 years ago we had a lad in our local club in NZ, who was a trier - but terrible.
He wore bright pink socks and tapped his foot all the time. We nick-named him Thumper or Pink Socks and although we tried to be polite, it was impossible to take him seriously. He bashed his guitar and sang like Dylan on a bad day. Lots of people were imitators then, trying to sound like Dylan or Donovan, Joan Baez or Judy Collins. I sounded more like Shirley Collins but not intentionally.
Most of the time we tried to sing like Pete or the Weavers.
Robyn