hmmmmm? Addiction is hard one. And being ex smoker of 5 years now I know first hand. Both my husband and i quit at the same time (intersting year between us). Your love and understanding is all you can really give. My best friend used to say things like " I can't belive you smoke?" Just saying that to me made a profound impact. Sounds wierd but when she said it was always with a worried tone. And she would say thingd like " you know if you quite now, your lungs would go back to normal in like 10 years. I quit when i was 33 years old. I think the younger you are the easier it is. You have the strength to exercise and work out any agressions. I started running. I had always walked. And now I ride.
don't pester your friend but drop helpful hints as often as you can without being annoying.
The reason we quit? I had kinda promised myself I would before I was 35 but it was hard cause my husband smoked too. But one day when we were going to Costa Rica for the first time, we were waiting for our plane and my husband said "I want to quit when we get back, no more "! He had never said that and I belived him. I asked why and he said he read a story that scared him. and that he wants to be here for me. That was enough for me. It was the toughest the first 6 months. But after a year it got way easy. I would never go back now.
She (or he) needs to find stuff to replace it. Hobby's, a sport, art what ever go into it full on. Riding and knitting help me a lot. I do enjoy at least 1 glass of wine every night. I belive in the power of one drink a day. Oh and Yoga is a huge help as well. I started before I quit, that is the way to go. You learn to respect your breath. And besides I could smell the smoke on me when i started to sweat (yuck)! Ok enough from me . Good luck, i hope you can help. Just be careful and don't drive them away!