I have an amateur couch psychologist theory why the smoking is pissing you off more than the infidelity: because one is cheating, but within the realm of knowledge you had about her, or a possibility. But smoking... sort of indicates that you didn't know her nearly as well as you think you did. And that's more disturbing than a person cheating (lots of people cheat at some point, and lots don't, but you get my point.)
Let's hear it for amateur shrink night!
