Run this by your wife.
So it was a good idea to be armed when carrying X amount of money? Yes.
What if it was Y amount of money? Well, yes then as well.
Well, isn't your life and well being worth more than that? It is to me!
I have never understood why people think it's okay to carry a weapon to protect "things" but not to protect people.
I think it's that theft is something that we can accept and insurance will cover but muggings, rape and murder are Boogiemen that are just to scary to consider and will go away if we just close our eyes.
I strongly recommend that you and her spend some time at http://www.corneredcat.com. She answers a lot of your wife's concerns as well as how to incorporate a weapon into her wardrobe.