I am a recovering peanut butter addict..
My mom made fudge just like your wife.. but my granny made it totally different... No Milk, but trade that for butter.
So after eating my grannys i cannot eat the milk version..
Here is the Recipe
1¼cups unsalted butter
1¼cups creamy peanut butter
Pinch salt
1½teaspoons vanilla extract
4½cups powdered sugar (sifted)