Hi there,
There can be many causes of vaginal discharge in girls. Sometimes this may be physiological, meaning it can be normal. However, this is only after other causes of abnormal discharge has been adequately investigated and infections have been ruled out or treated appropriately.
If you sister has been having this daily for a few years, it would be advisable to get the symptoms checked to ensure there is no underlying infection that has been left untreated for a long time.
Regards,
Dr Michelle Chia