I smoked for several years after my wife quit. She would comment once in awhile that she knew I just had a cig when I could not smell anything at all. She was really good about it though as she never did this in a way that made me feel bad or guilty. I always tried to be careful about smoking around her though because I respected the fact she was now a non-smoker and likely more sensitive to the smell of smoking.
I'm not sure there's any way to approach this with your wife in a manner that won't have her all up in arms about it. Smokers get pretty defensive about stuff like that - I know I did and I suspect you probably did too. More and more smokers are the outcasts of society these days so when your significant other starts in on you ..... look out.
If she is respecting your situation, in terms of not smoking openly around you and subjecting you to her second hand smoke on a regular basis, I would say that's probably the best you can hope for until she too is ready to quit. That may just happen too as you are setting a great example for her