Marriage some times is a compromise. Show her what you can safely tow with a single, and then show her what you can safely tow with a dually.
Your wife has to understand that there is a limit to what each truck will tow.
She might be willing to make a sacrifice in floor plan to use a smaller truck. Just remind her that 95% of your time, you be in the trailer, not in the truck.
I was lucky. My wife has a higher class of driver's license than I do as she drove bus. When we road tested our dually, she took it to an empty parking lot, checked parking it, then she checked the turning radius when doing a "U" turn. It passed her tests, so she said: "This one will do." It has been a great truck.