Re: In need of good books for 8 year old girl
Where the Red Fern Grows
Dark is Rising series
Hank the Cowdog
Left Behind Kids (based on the Left Behind books, but featuring kids)
Esperanza Rising (and other books by the same author)
Misty of Chincoteague and others in that series
I could probably come up with a few dozen more if you need, but those were the ones my oldest liked most at that age. You should also check out the Newberry Award books and ask the librarian.
There aren't a lot of long books at that age. Mostly you have to look for more challenging content, not longer length.