Please correct me if i am wrong - your sister had a bad episode of pneumonia
at the age of 1 year, and not since!
She however has developed allergic asthma
and gets pains in the chest where the pneumonia had occurred.
It is unusual for the pain to be related to the previous pneumonia episode, unless she has had further lung problems and has left lung scarring, in medical terms this is known as fibrosis.
can lead to several complications, and if there is evidence of bronchiectasis
on HRCT scans, pain in that area can happen as sputum production continues and the constant cough leaves one with pain.
My suggestion would be to get proper investigations done, such as HRCT Chest, lung function studies with DLCO (that shows the current lung function with regard to oxygen diffusion) and get these reviewed by a Chest Physician.
can also be a possibility if there has been a recent fall, and the CT will pick this up as well.
Please ensure that the asthma is also optimally controlled. You can ask her to do the ACT (Asthma Control Test) online to see the level of control.
Hope this helps.