First off, welcome to HGF!!
The fact that you are 64 (old enough to be responsible) and don't have any little kids running around, it shouldn't be too much of an issue. Have you discussed it at all with her?
Remind her that you already have guns and one of them is a pistol. This is just a different one
I think the shotguns could be just as dangerous in the wrong hands.
Also, start off by telling her how much you love her. "hey baby, you know I realy love you, right?"