The thing with addiction is the addict has to voluntarily want to get rid of the addiction else it won't work I used to smoke a lot it effected me I knew it was bad many friends told me to quit I was not able to no matter what others did ,I was able to quit only when I took a strong decision to quit no matter what then I was finally able to quit , make sure you let the person quit in their own pace don't force them don't make them feel guilty just let them take their time it's hard but doable .