The Dark is Rising series by Susan Cooper. I've read them all again at least twice as an adult. They might be a year or two too old for her right now in terms of literary complexity, I'm not a good judge of what a 3rd grade reading level is.
Others childhood books I've pondered checking out from the library again recently are the Princess and the Goblin (can't remember the author) and The Last of the Really Great Whangdoodles by Julie Andrews. I also liked The Little Princess. I don't remember liking the Secret Garden as much.
