Thanks for using HCM, I understand your concern and will try to give you my medical advice, I think your daughter have some viral infection because she has a negative chest X-ray and the antibiotic doesn t work, mostly all respiratory viruses are autolimited that s means that they destroy itself, she could have a viral pharyngitis an the treatment is focused to relieved symptoms, you can use some OTC medication like antihistamines, acetaminophen, drinking plenty of fluid and some warm salt water gargle, try to keep a free environment from chemical or odors, I hope that my advice help that your daughter get better, regards