Thank you for asking your query.
There are many things you can do to prevent Tuberculosis being transmitted from your wife.First and foremost thing is getting proper and complete treatment for your wife. Withing few weeks of treatment the bacteria which spread via cough droplets will come down drastically. Treatment of Tubleculsis is a longer process than other common infections but a complete cure is possible in most of the cases. So support your wife and motivate her to take the drugs regularly and till the end of the prescribed duration. This is the most important step in prevention.
The patient can cover her nose and mouth using a piece of cloth during coughing and sneezing. If some kind of isolation is suggested by the treating physician she should adher to it. The procedure are different in each countries. For example in places like China and India, where TB is epidemic patients are almost never isolated. This may not hold true in US and other western countries.
I would also recommend you to stay in good heal, eat healthy food. If you have any co morbid conditions like Diabetes it should be given due importance and treated accordingly.