She has had chest X-rays before... Nothing showed up. Yes, she has allergies. I gave her some of my Claritin and it seemed to help a little. The cough wasn't as bad. Really the only day time symptoms are is she exherts herself. She might have a little coughing but nothing like at night.
Asthma often acts up for a lot of people at night. It often manifests with cough, wheezing, chest tightness, shortness of breath and for some of us we get a lot of mucous too. I would suggest she see a doctor about this if this isn't the first time. pulmonary function tests can be ordered to determine the cause of her symptoms. Sometimes a chest x-ray is called for if the doctor suspects something other then asthma. Does she have day time symptoms too? Does she have allergies? If the symptoms are interfering with her every day life, then it is a good idea to get to the root cause of it all.