More details.
An all state OPAC research in Germany got me one copy in another state library where the book was published and - three copies in our English department. Sometimes it is good to be a librarian in a univeristy library.
As I presumed the book is a collection to accompany English lessons from the beginning (10 years) to high school level (19 years). It contains
103 songs, a few in two or three parts:
Folk songs: 33 ; rounds: 43 ; Ballads: 7 ; shanties: 5 ; spirituals and plantation songs: 9 ; madrigals: 6

It was published by the Pedagogic Research Dept of the Free Waldorf Schools Association (Pädagogische Forschungsstelle beim Bund der Freien Waldorfschulen) in Stuttgart. The Waldorf Schools are part of the Anthroposophy Movement founded by Rudolf Steiner, of Austria.

No ISBN given; not in the German equivalent to Books In Print.

So I think your friend Jill should try the Rudolf Steiner College in Fair Oaks, CA.

I hope this might be helpful for her, more I couldn't find out.

Cheers
Wilfried