Probably because she was then faced with a return flight! What would she do with the gun. I’m sure she wanted to keep it and figured the only way was to declare it and they might possibly help her get it back home?
Just a thought!
All she had to do was get a plastic gun box for $10 at any gunstore or walmart, lock it and put it in checked baggage. Declare it at time of check in for return trip, and it travels back home.
The way she did it, she is out a $300 gun.