Indigo Airlines — boarding not allowed and staff behavior

Address: Patna, Bihar

My friends flight was booked from patna to bangalore. Web checkin was done. She was present at airport prior 45 mins to depature.in the display your flight status was showing security check. After waiting for 15-20 min i went to check if boarding has started they said that the boarding is closed and flight has moved prior time. Can you please explain if you had started the boarding of passengers why was it not displayed and how can a flight leave before time without boarding the passenger who has done web checkin.
Your staff at patna airport was so rude, she did not even listen to to what my friend was saying.
Kindly look into the matter.

Regards
Samir kachhap