If she was mad about it, just be like "Look mom, they're just cigars. I like to just smoke them with my friends during special occasions. I promise that I won't get addicted to them. I know that it is illegal, but I feel that I can use them responsibly enough and not get addicted to them. If you let me smoke them, I promise to respect your house rules and not smoke them inside, or even where you can see them. It's just relaxing to go out with a few friends and smoke a cigar or two while I'm playing poker. At least they're just cigars, right? At least I'm not drinking or doing anything else, you know? They're relatively harmless."

She should be cool with it if you just approach her in a mature manner.