Castle Doctrine is Maryland, does not cover only your "residence", it also covers anywhere you stay temporarily, such is if you were on a trip in Maryland, and someone breaks into your hotel room while you were on a overnight hunting trip per se.
As for the other sentence, you need to feel comfortable what goes on at her place.
People are strange and they can do stranger things, than what you could ever dream up.
What are the laws regarding me storing the shotgun at her place, provided it has a Maryland DOJ approved internal lock?