Take her to your family GP for a thorough check up. If tests cannot find any real cause for her nausea then it could quite possibly be something that is bothering her. Any bullying issues happening? One of my neices picked up on her mother's radical dieting saying she didn't want to get fat like her grandmother. She started not eating also as became fixated on not getting fat. This was during her parents break up also, so it then became her way of gaining some much needed attention. She never did put on much weight, always thin, and her younger sister who idolised her also started to follow the same pattern. Think about what your daughter may have overheard, whether her parents, other adults, caregivers, friends etc. They can pick up simple conversations and take them quite literally. Schools at the time here were so very focused on healthy food eating I think they may have over-emphasised eating problems too. They meant well but children can be too easily influenced.