I can't advocate keeping secrets from your spouse. Regardless how many bank accounts you have, you need to come to an agreement on what you can spend on camera gear and what she can spend on worthless stuff like =SUM(clothes,shoes,makeup,haircareproducts,jewelry,etc). 
Still, it would be hard to prove that the 7D would make better pictures than the perfectly good T3i that you already own. Specs and reviews are meaningless unless/until you have the skills to get the most out of a camera.
Keep your eyes open for a nice used 5D Mk II. Despite its obsolescence, it's a friggin' amazing camera that will actually make use of the 61% of the lens image that your current camera wastes. Here you can show your beloved bride the difference:
T3i image:
5D Mk II image:





(or not any for a looonnnggg while
