Please forgive the delayed reply. I haven't had much time lately. Thank you for your questions. I'll see if I can answer them. I seriously doubt that she was at all concerned that if she quit smoking it might somehow affect our friendship. We have known each other for too long and have always been too supportive of each other for that to be a concern.
Smoking is a significant part of a smoker's life, and it is only reasonable that she would want to talk about potentially making such a major change.
I believe that her comment about using my health as a bellwether for when she needs to quit is gallows humor good-natured chiding me for being a heavier smoker than her. For as long as we've known each other, I have smoked roughly twice as much as her, so the joke has been that it would kill me twice as fast. Speaking with her on the telephone a couple of nights ago about an upcoming wedding in which we are both participating, she observed that the black dresses we'll be wearing "Will match our lungs." I think my friend may be getting in touch with some latent dark attractions to smoking.
If either of us detected something in the other's health or lifestyle that disturbed us, we would be direct and say something about it. We have done so before and I'm sure we'll do so again. As for my overall health, I haven't detected any changes that concern me and I tend to be very aware of such things.