It is quite unclear as to whether Alyson Hannigan smokes cigarettes in real life of not. She certainly has smoked as part of her character on shows in which she’s been, but her real-life cigarette-smoking status is unclear, as there is evidence either way.
Now the picture above is clearly taken from a TV show, so it is no proof that she smokes. If she has managed to gravitate in that industry for all those years and not pick up this disgusting and deadly habit, good on her! And if she does smoke cigarettes, well it’s never too late to do the right thing!