I recently visited a K-8 Montessori School and love their methods. They combine first through third grade into one classroom, fourth through sixth grade into another class, and seventh and eighth grade into the oldest class.
Kids also learn at their own pace.
A. Montessori programs can be wonderful for gifted children, especially given your daughter's needs. At this point, however, we can't know what to do then. It will depend on what her needs are, and what the options are. A lot can change between now and then, so it's better to look at her needs today and see how they can best be addressed. You'll be able to watch her grow and can plan further along as her needs change.