Hi S. K.,
Thank you for your query.
By your description it appears your niece is feigning that she is not able to listen. It is advisable to show her to an ENT doctor who will conduct an audiometry
test to know whether there is any auditory loss. If there is no auditory loss then she may need pyschological assessment to know the reason for feigning. Most probably she may not be prepared or has lost confidence for the upcoming board examinations and is behaving in this manner.
I would not be able to suggest any doctor either in Kolkata or Ranchi but any ENT doctor should be able to organize an audiometry test on your niece.
I hope I have answered your query to your satisfaction.
Wishing your niece an early recovery.