Spot on lungs?? help??!?

My little sister (9 turning 10 soon) has had a really bad cough lately. My mom took her to the doctors and they said it was bronchitis and gave her an antibiotic. 2 weeks later she still has the cough (a little worse) so she went to the doctors again. she sent her to get an exray and it looked pretty normal, except a "spot". I am worried because sometimes she...