I recently had a request from a parent for reading recommendations for her nine-year-old who is a very advanced reader and writer. I thought I would share what I came up with...
For writing guides, I would recommend a pairing of the sublime and the ridiculous. In my opinion, every serious writer, no matter what age, should have a copy of Strunk & White's The Elements of Style. I think the illustrated version, with Maira Kalman's zany visuals, would be perfect. That's the sublime...
For kicks, I also think your daughter should take a look at Dan Gutman's My Weird Writing Tips. Much of his information will be old hat to her, and some of his assumptions are for the writing-averse reader, but I think his chatty tone is fun and his lessons about revision, character, plot, and perseverance are good reminders to all writers. It will also help her feel super-confident because she will recognize topics and good practices.
Another book I just got in with writers like your daughter in mind is Thrice Told Tales: Three Mice Full of Writing Advice. The author uses the familiar nursery rhyme to illustrate literary devices and analysis. It's unique, clever, and easy to understand without talking down.
As for novels, I'm a big believer in letting readers follow their bliss, but I also think it's great to provide books that are challenging without being emotionally inappropriate. (I have to confess that I read way outside most parents' comfort zones when I was growing up... I realize now that I glossed over things I wasn't ready to confront, and reading beyond my level helped sate my curiosity so I stayed home reading throughout my adolescence rather than experimenting like some of my friends!)
For advanced readers, I always recommend classics. The Swallows and Amazons series, the Anne of Green Gables series, books by Frances Hodgson Burnett, Little Women are all great. Anne's love of literature and Jo's writing might be particularly appealing! (Montgomery also did a fantastic series about Emily, a girl who grows up to be a writer, but it's just a little darker and gets into romantic plot points earlier than Anne.)
So many families read the classics aloud early to children with great listening comprehension, and sometimes that means the classics get overlooked when the readers are at the right age to read them alone. I never underestimate the power of rereading! Especially for writers, familiarity with a text is not a bad thing.
Another fun idea would be read-together pairings of classics and recent books inspired by them. Among these: the Narnia books paired with The Twistrose Key; A Wrinkle in Time with When You Reach Me; The Adventures of Robin Hood with Will in Scarlet. These are books I love on their own, but I think a young writer can benefit from comparing to closely observe how stories can be retold.
Along those lines, there are many retellings of fairy tales and myths that could be interesting to study. One of my favorites recently was Rump, the story of Rumpelstiltskin told from Rumplestiltskin's point of view. Very clever and entertaining!
As you might have guessed, I might be able to go on for hours... but I'll stop here.