Both of my kiddos are very expressive readers as well. However, DD10 got very shy about reading aloud beginning in maybe mid-second grade. Not really sure why that is, but I suspect that as she listened to other children read, she became aware that she sounded different than they do and didn't want to sound "adult" or different. It is definitely pretty unusual for children in general (not speaking GT here) to be very expressive oral readers. Even those who are fluent readers tend to be flat in their read alouds--phrasing is good, tone generally matches, but the magic that makes books come alive is absent. See if she'll let you videotape her reading to a younger child, stuffed animal, etc... I really regret not capturing it when DD was younger!