Explain. I don't see how this is possible without cameras or fingerprinting. Maybe leaving a wheel safe on a certain digit each time would work.
Gun safes are intended for thieves, small children or maybe to stop acts of passion. They are useless for securing something from a calculating adult that lives in the same house.
I don’t know about useless - a locked door is useless if your philosophy is that someone can kick down the door.
However she needed to meet her responsibility to make sure her firearms didn’t fall into the hands of a psycho - my point is that she FAILED in that responsibility.