A few more I just thought of that she may be less likely to have as they are a bit older:
an excellent Arthurian fantasy series called The Dark is Rising by Susan Cooper
Astrid Lindgren! Ronia the Robbar's Daughter, Pippi Longstocking, etc
Tove Jansson Moomintroll series
Philip Pullman (author of Dark Materials trilogy - that series is brilliant!) also did several wonderful girl-protagonist adventures: the Sally Lockhart Quartet
https://www.philip-pullman.com/books/the-sally-lockhart-quartet/