You know this is interesting. I do not have a gluten sensitivity, as far as I know, but when I go to my pantry and fridge, I really don't find much gluten.
It is possible to avoid it and not substitute something else. I mean, the biggest culprits are the entire bread category. So you cut out your daily sandwiches, your crackers, your pretzels, your pasta… once it isn't a habit though, I don't know, it is easy not to miss it.
Instead of trying to figure out how to "get rid of" or substitute something else for gluten, I'd seriously encourage your wife to start eating completely differently. I'm sure you've heard of the paleo- or "cave man" diet. It is basically protein, fruit/veggies, nuts, berries, etc. Things a cave-man would have eaten.
It can be virtually gluten free. A lot of the gluten you find inside your fridge comes in the form of additives to condiments and salad dressings. So, start seasoning food with more herbs and spices, dress salads in oil and vinegar, top off a great meal with another veggie instead of adding that garlic bread. Again, once you cut it out, I've personally found I don't much miss it.
And once you are out of the habit, you start to know what kinds of food choices to make, so that even at a restaurant you can easily order off a menu and not have to ask for special treatment.