Well, thanks to everyone for their insight.
To be fair, I am riding a perpetual roller coaster of emotions and it seems the simplest of questions can tip me off.
I realize people have an inherent need to quantify their decisions in light of awful things happening around them. Yes she smoked, probably because everyone she knew smoked, including doctors. Do I wish she hadn't smoked? Of course, because maybe that caused her cancer. But her illness is no less tragic than if it occurred to a non-smoker.
To be fair, however, my mother-in-law smokes. After not having seen her since we learned about my mother's cancer... well, next time she lights up, I can imagine my blood will boil a bit.
Thanks to this board for its continual support.