I think DD was a little older than 6 when she read the Guardians of Ga'hoole series, but not much older. I think it was in second grade that she and her buddies spent the whole school year being owls on the playground! Anyway, if your DD can read "up" level-wise, these might be fun because a movie of the first one is coming out soonish.
Along those same lines, Kevin Oppell's SilverWing series is another well-loved one here. Again, maybe a little above-level, but I've found that an exciting storyline will bring a reader along even if it is a little harder than what they are used to.