Has she read The Phantom Tollbooth? That's definitely one that's worth checking out. I can never remember what books are at what reading level, but I'm pretty sure it's age appropriate.

Honestly, I've never had a taste for most sci fi either, I've always found it much harder on my suspension of disbelief than fantasy. It's one thing for me to accept a setting that runs on fundamentally different rules, but when a story that's nominally set in our own universe differs from our own in implausible-seeming ways, my instinct is to call bullshit. Sci fi scenarios always set off my implausibility alarms because they weren't weird enough, they're mostly just modern society plus developments in a single metric along a single dimension.