I respect their judgment on the ones I haven't read and concur on the classics, and would add that she might enjoy a trip to Venus with Podkayne Of Mars by Robert A. Heinlein.
I don't think you can harm a child by giving them challenging reading, especially if you have a budding bibliophile.
“I don’t think you can harm a child by giving them challenging reading, especially if you have a budding bibliophile.”
Agreed. The more challenging, the better. A “budding bibliophile” is probably a good descriptor.