She could try and mail order sheet music from
this company in Berlin.
They stock a lot of folk music, and they can order abroad as well (they're the German distributors for Mel Bay books, for example).

As for teachers: I've had the same problem here in Bochum. Thought I'd found a teacher, because he did say he would like to teach me folk music, but he then cunningly switched to teaching classical music after a few weeks only(after the proof time). Needless to say, I left him.
All I can say is: ask around! Put up a notice in Irish pubs and at the university campus in Bonn (most violin teachers who like teaching folk/blues/other non-classical styles are a bit younger, strangely enough).