My wife just finished reading The Wild Robot with my son (6) and they both really enjoyed it.
Books
My 8 year old granddaughter loves books by Mo Willems.
And Goosebumps.
Marguerite Henry horse books.
If she likes wordplay, The Phantom Tollbooth.
https://www.weareteachers.com/books-for-6th-graders/
There’s lots of interesting looking books at the link above, but you and/or your daughter could check with the librarians at her school or at your local libraries to get more tailored recommendations by giving the names of her favorites and what she’s finding too scary or sad. Librarians LOVE to match readers with books.
Peter and the star catchers is around 500 pages ya and about Peter Pan and Neverland and the author is arguably one of the better fantasy ya writers. He has a whole series set in Disney land or Disney world called the kingdom keepers
Also two series that might work or will soon:
The Fairyland Series by Catherynne M. Valente
The Wayward Children Series by Seanan McGuire
The Last of the Really Great Whangdoodles! It was one of my very favorite books at her age!
Black Beauty may also be good for her. There are a few scary parts but it ends well.
She may like the American Girl books, too. My favorite series were Felicity and Molly, but all of them are good.
Harriet the Spy
The Wishbone series
The 39 Clues series
The Far Side of the Mountain
The Little Princess
The Secret Garden
The Magic Treehouse Series
Gone Away Lake series. Its wonderful for that age group. I read it with my kids and enjoyed it as much as they did!
I loved the American Girl series at that age.