Hi and welcome to the forum. People here are great and very supportive. I read your post and wanted to answer, I dont know if it will help or not. I am 58yrs old with Stage IIIB lung cancer and I still smoke. (Just dont have enough common sense to quit). Dr also told me that quiting will NOT change the outcome. When I was first diagnosed, I smoked maybe 1/2 to one pack a day. Well after I got the FINAL diagnosis and knew what was going on, believe me I smoked like a chimney. I know now it was nerves, tension, stress, and the unknown. The cigs calmed me down. I smoke like one after another. I did this for about a month. When I finally made peace with myself, knew what MY goals were and what the future may hold, I finally cut down again. I now smoke maybe a pack every two to three days. I know me and I do know that I will probably not give them up. Give your mom some space and let it be HER that decides to cut down (with no pressure from someone else). And I do believe that down the road something will click and she will relent on them some.
I dont know if this helps any but it may. Everyone is different and have different strengths within themselves but wanted to let you know from a still smoker here.
I wish you the best. Like I said, everyone here is great. Ask questions, vent or just read some of the posts here.
Bless you and yours......