Tell her that she can get something that she really wants if she agrees to stop smoking for one week. Better yet, start with 3 days. There has to be something that she has been wanting. Then make the rewards bigger and bigger. If she can go for one month get her a massage or something similar. If she goes for 2 months then a day at the spa or something like that. My wife is always hinting about spa days or a new purse or something. Don't wait until it is too late. I was put on a pulse oximeter
when my heart got too bad from prolonged smoking. It was enough motivation for my wife to try and stop. Good luck with the motivation, it is a good thing to stop smoking.