Nausea, abdominal pain around the belly button, bad sleep, maybe even itching around the bottom are common symptoms of a parasite called pinworm/threadworm. This parasite is sadly very common, especially
in kids. It is usually easy to get rid of, if you follow some strict hygiene measures, and get the tablets from the GP. Give her lots and lots of raw grated carrot to eat, as well as fresh pineapple and raw pumpkin seeds. Reduce her sugar and carbohydrate intake for a while.