The simple answer to this question is no, nuns are not allowed to smoke. However, there is a bit more to it than that. While the Catholic Church does have strict rules against smoking, they are typically directed towards clergy members and religious figures who are in positions of authority. This means that while nuns technically fall under this ban, it is not always strictly enforced. In fact, many nuns actually do smoke cigarettes, though they usually do so discreetly and away from the public eye.
There are a number of reasons why smoking is discouraged for nuns (and other religious figures). For one, it goes against the principle of living a healthy lifestyle. The Church wants its members to be as healthy as possible so that they can better serve God and the community. Additionally, smoking is seen as a luxury and an indulgence, something that should be avoided if possible. Finally, smoking can be addictive and lead to other unhealthy habits, which is why the Church wants its members to steer clear of tobacco products altogether.
Despite all of these reasons against smoking, many nuns still choose to light up on occasion. It's important to remember that while they are bound by certain rules and regulations, they are also human beings with their own desires and weaknesses. Ultimately, whether or not a nun smokes is up to her own personal discretion – but it's safe to say that it's not exactly encouraged by the Church.