Hi Your daughter is probably suffering from chronic sinusitis.It is a condition that can be very disturbing and resistant to most medications if not handled well.The condition always interferes with mucus drainage and always cause mucus build up.It could be caused by an infection, growth in sinuses or nostrils like nasal polyp, deviation of the nasal septum or allergies.It may at times give thick and discolored discharged from nostrils and this can explain the greenish mucus you saw.Treatment however will depend on the cause of the condition.Some lab and imaging investigations may at times be needed to know the exact cause: nasal endoscopy, CT scan, nasal and sinus culture, and allergy test.Depending on the identified cause, treatment options may include: saline nasal irrigation, nasal corticosteroids, oral or injectable corticosteroids, antibiotics, immunotherapy, and surgery if caused by a tumour. With all these possible causes and treatment options, i will advise you see an ENT(Ear, Nose and Throat) specialist for evaluation and investigation. In the meantime, the following home measures may help relief you: -Rest -Drink enough fluids -moisturize your sinus cavity at times with vapor -Apply warm compress to your face -Rinse out your nasal passage occasionally -Sleep with your head elevated Hope my answer will help you Best regards