I am fairly new to the wife being interested thing. For me her interest in personal defense is some what a surprise. So, I have had to work through a lot of these questions.
Some will tell you what they think you need to do for her. Others will tell you to let her choose. You need to know your wife. Mine is independent, stubborn and insists that every thing was her idea. So, I couldn't tell her this is what you need to do, this is what you want and here is how you use it. Her interest would just drop.
I did choose her weapon, but only because it was a mother's day present. Even though I pick it out, she did the final payment on it. Also, it would have been much quicker for me to present my conceal permit to buy it without a background check, but then it wouldn't be hers.
Also, I can show her the basics and I do insist on safe practices, but my plan is not to train her. On the other hand, I will gift her classes with professionals. I will gladly take the kids and even take her out that night to celebrate whatever.
Now, I have to get permission to take her gun. She insists that I buy my own ammo for it. Here is the best part, she requires that I clean it right away. Now, she takes responsibility for hers and my kids defense and is not my gun stooge. As much as I would like to teach what I know, I love that she shares what she knows.
She loves her sp101 and shoots 38s. She doesn't like the .357s, even I think they bite a little, but I like the bite. A main reason for choosing this one is that it is a point and shoot gun; no fumbling with chambering a round or stove pipes while she is carrying a baby or anything else on her weak side.