I always knew that smoking caused a risk for low birth weight, but I was TTC for a long time before discovering that it could have other effects like speeding menopause. I'm part of that generation that looked at our moms and said "well they smoked and drank the whole way through and we seem to be okay!" Of course, my mom was 22, but w/e! I sort of thought I knew it all about smoking and babies.
So for what it's worth, I don't think I'd necessarily assume she knows all the effects. She might be thinking it's only risky once the BFP happens.