Early on she said she smoked for a while (before we met) but had quit. This weekend the topic of my grandparents came up and I mentioned how both of my grandfathers died from lung cancer so I'm pretty anti-smoking and I want it nowhere near my life.

In the past she's asked me if i'd ditch her if she got fat. (to which i responded "i'm certainly not sticking around if I care more about your well being than you do. and she said she felt the same way which was a problem she had with her ex getting fat blah blah blah...")

Anyway, we've had a few drinks and are walking home and she randomly admits it's not unusual for her to bum a smoke when she's hanging out with her mom, which is once every 2 weeks or so.

I more or less said I don't like that and want her to stop, to which in so many words she said "That makes sense. I won't do it anymore." Knowing her, she was seeing if I was actually going to actually state the boundary or just laugh it off. I'm still not sure how to proceed since I've never run into a problem like this before.

The fact that she wasn't completely honest in the beginning is also a bit of a worry, but that's a whole different story...

I'm glad she was honest (albeit while drunk...) so punishing her for it wouldn't have been the right move. At the same time, it's obviously not like it's difficult for her to hide and I can't force her to stop.

So far I've landed on just letting it go but if I get any signal she's been smoking again, withdrawing. But what would you do/have done in this situation?