Ahhhh....but it appears that she hasn't been able to hide it or else he wouldn't be aware of it.

Some excerpts below from research-based government info on smoking and smoking cessation....

From the Centers for Disease Control:
What if a person smokes again after quitting?

Many smokers find it difficult to quit. People commonly quit smoking and then find themselves smoking again, especially in the first few weeks or months after quitting. People who smoke after quitting should try again to quit. Most people find that they need to persist in their attempts to quit smoking before they quit for good. It may take four or more attempts before smokers are able to quit for good. People who stop smoking for 3 months or longer have an excellent chance of remaining cigarette free for the rest of their lives.

From the National Institute on Drug Abuse....
Is Nicotine Addictive?

Yes. Most smokers use tobacco regularly because they are addicted to nicotine. Addiction is characterized by compulsive drug seeking and abuse, even in the face of negative health consequences. It is well documented that most smokers identify tobacco use as harmful and express a desire to reduce or stop using it, and nearly 35 million of them want to quit each year. Unfortunately, more than 85 percent of those who try to quit on their own relapse, most within a week.

Research has shown how nicotine acts on the brain to produce a number of effects. Of primary importance to its addictive nature are findings that nicotine activates reward pathways—the brain circuitry that regulates feelings of pleasure. A key brain chemical involved in mediating the desire to consume drugs is the neurotransmitter dopamine, and research has shown that nicotine increases levels of dopamine in the reward circuits. This reaction is similar to that seen with other drugs of abuse and is thought to underlie the pleasurable sensations experienced by many smokers. For many tobacco users, long-term brain changes induced by continued nicotine exposure result in addiction.

Are There Gender Differences in Tobacco Smoking?

Large-scale smoking cessation trials show that women are less likely to initiate quitting and may be more likely to relapse if they do quit. In cessation programs using nicotine replacement methods, such as the patch or gum, the nicotine does not seem to reduce craving as effectively for women as for men. Other factors that may contribute to women’s difficulty with quitting are that withdrawal may be more intense for women or that women are more concerned about weight gain.