I can understand why your wife wouldn't want your daughter being exposed to smoke. But if she's worried about your daughter taking an interest in smoking, I'd say there's nothing over which to be concerned.
Kids are curious about everything that their parents do. If they see you watching Antiques Roadshow, then they'll want to watch Antiques Roadshow. The problem is that if you tell them "no," they'll just want to watch Antiques Roadshow even more.
Now, catching your kid smoking is not quite as shocking as catching them watching PBS programming. The best thing you can do is kill the curiosity.
At our gun shop, we have a lot of parents who buy their first gun, but, similar to your situation, get nervous about their kids getting curious and searching around for the gun when the parents are sleeping. My response to them is always: "Let them see it and handle it under your supervision after you've made sure the firearm is safe. While you should definitely keep it locked up at all times, tell them that they're welcome to look at it and handle it whenever they want under your supervision. All they have to do is ask, and you'll never tell them 'no.' And tell them that maybe one day, if they like, you can take them shooting with you. Just, whatever you do, don't try to shelter them from it and don't tell them it's 'not for[them].' That first day you show the gun to them can (and usually does) end their curiosity right then and there; if you keep it a secret saying it's 'for adults only', you're much more likely to have them constantly hunt for it which could lead to an accident."
My advice as an educator: the next time you smoke, give her an empty old cob pipe to hold while she joins you. She'll eventually realize that it's not exciting and eventually take an interest in something else.