Is "Babysitter's Little Sister" series around? it was a spin-off of the "Babysitters Club" series, same author but written for younger readers. Good stuff.
I always make a point of reading what the kids read - I can whip through a little kid's book in a fraction of the time they take and once I've read it I can discuss it with them, ask them what they think of what this character said or did, basically workshop it with them.
If you get to the stage where she'd read everything apparently available, go read your own way through the childrens' shelves.
Classics that come to mind - Dr Dolittle (Hugh Lofting). "My Family and Other Animals" by Gerald Durrell (a lot of fun, maybe a bit challenging but within the range of a bright, well-read 7 year old).
And my absolute favourite author - Terry Pratchett. He's written the "Discworld" series of books for adult/older readers, they've been described as "Tolkien on acid", it's fantasy satire. But he's written some lovely stuff for kids. I would strongly recommend "Wee Free Men" which difficult child 3 is close to finishing (difficult child 3 finds reading ANY fiction book a challenge). Read this book aloud to her, you will enjoy it too. It's about a young girl whose baby brother gets kidnapped by the Queen of the fairies (who is NOT a nice person) and who has to go to rescue him, even though she doesn't like him very much. On the way she is helped by some "Pict-sies" who are like a band of miniature Billy Connollys. It is safe topics for children, although you might worry, with the Pictsies as they're a rough lot, who got thrown out of Fairyland for being drunk & disorderly. Tiffany lives on a farm and wants to grow up to be a witch, like her Granny. In this 'universe' witches are more like the Wise Women of folklore, the ones who help at the coalface of humanity.
There are another two books in the Tiffany Aching series - "Hat Full of Sky" and "Wintersmith". They are funny and thought-provoking books.
Another suggestion - see if you can find "I, Robot" by Isaac Asimov. They are short stories and should be readable as much by a child as an adult.
I'll keep thinking, see if I can come up with more.
Marg