DD9's school does AR. Since our district's schools are such that all 4th and 5th graders attend the same building, the libraries have a limited selection of above grade books. DD is currently in 6th grade accelerated Reading with other GT 5th graders. Her teacher suggested that her students can either a) do the AR quizzes for points or b) complete a book report after finishing another book. She knows that most kids that take the accelerated LA are eager readers and don't need the points to motivate. Maybe this would be something you can suggest to the teacher, if you child is willing to "give up" the AR points to get more motivating books. I know DD was.
I also second looking into grade skip. If you begin to pursue this option now and the school is willing, doing the skip after holiday break might be a good fit. January is a lot of review anyway, so that would help her get up to speed.
Jen