There are so many great books at the 4th-6th grade level. I wouldn't skip them just because she can process harder stuff. My DD can read pretty hard books, but it's really important to me that she experience the "canon" of great children's literature...
Yes, and more so, these books will tend to deal with relevant themes related to growing up.
If you're just going for complicated plots, do the Warriers books and other mega series. However, if you are going for more insight into the human condition and good writing, work your way through the Newbery Award and Honor books, and Newbery winning authors. This recommendation came to us from the psychologist who did DD's neuropsych exam in which he diagnosed dyslexia/dysgraphia. Newbery books are GOOD WRITING, giving a solid model for writing styles and use of language.
In the last year, we've listened to:
Harry Potter 1-3
From the Mixed-Up Files of Mrs. Basil E Frankweiler, E.L. Konigsburg
A View from Saturday, E.L. Konigsburg
The Outcasts of 19 Schuyler Place, E.L. Konigsburg
A Door in the Wall, Marguerite de Angeli
The Penderwicks, Jeanne Birdsall
The Tale of Despereaux, Kate DiCamillo
Scat, Carl Hiaasen
The Lightening Thief, Rick Riordan
A Wrinkle in Time, Madeleine L'Engle
A Cricket in Time Square, George Selden
The Phantom Tollbooth, Norton Juster
21 Balloons, William Pene du Bois
Around the World in 80 Days, Jules Verne
The Railway Children, Edith Nesbit
Centerburg Tales and More Centerburg Tales, Robert McClausky
A Christmas Carol, Charles Dickens
Cheaper by the Dozen, Frank and Ernestine Gilbreth