Steffie Lerch was - I believe - a German illustrator of books. I haven't been able to find any information about her other than bibliographies. If anyone knows anything about her, please let me know and I will update my post accordingly :)
I know that she illustrated two much loved books. "Heidi" and "The Surprise Doll" ("Søndagsdukken" in Danish).
These images are from the latter.