My 13 yr old girl has cheat pains and dry throat. ekg and eco were normal last month should she have a chest x-ray?

Cough: It is probably not likely that anything will show on the xray. A persistent dry cough and chest pain, in that age child is more likely to be signs of some type of bronchospasm (asthma). I would recommend a pediatric pulmonologist. :)

Allergy/asthma: I would recommend a pediatric allergist for formal alllery tests and lung testing for check for asthma.