From what you have mentioned, its almost 15 days over now. I can understand your worries.
Apart from fever, chest pain
you have not mentioned any other problem like cough, cold, breathing difficulty, urinary problems etc. Also you have not mentioned the site and details of chest pain.
Also you have not mentioned about her activity and food intake.
But I would suggest to take your child to a good center and if needed to hospitalize her.
Have her re-examined and re-investigated.
Complete blood count
, CRP, WIDAL, Urine microscopy, repeat x ray
chest can be done as base line investigations. Based on the reports and condition of the child, further investigations can be done.
Usually kids with Pneumonia
if treated with appropriate antibiotic get okay by 4 to 5 days. Though X ray abnormality may persist for a month, fever etc will subside soon. Since you say fever has reappeared with chest pain, one needs to rule out complications of pneumonia like pleural effusion/ empyema
Don`t panic. Calm down, be courageous and get her treated.
Hope my answer helps you.
Wish a speedy recovery for your kid.