As far as Billie Piper vs. Karen Gillan goes, I was really disappointed to learn that Billie Piper smokes, too. In both cases, frankly, I find their characters -- Rose Tyler and Amy Pond -- much more attractive than their actresses, precisely because of that point.
You're assuming, of course, that neither of Rose or Amy smoke...
I don't know, what does the evidence say? I'm not calling B.S. on the health risks of second hand smoke on that count I am on the fence until pointed to evidence either way. I'm calling B.S. on your reaction to it, I think it far more likely that your reactions to smoke have a large psychological element.
Several links here
. While I may find people's reactions to this a bit amusing, smoking really is one of the more awful practices people engage in.