Hi cocoa: Nicotine is addicting, just like cocaine, heroin or alcohol. In fact, it may be even more addicting than cocaine (some studies have suggested it is. It is very hard to quit smoking.
Your mother is also in denial (many addicts are). Addiction is real, it isn't just a choice, it may start out that way, but it becomes addicting. Really, truly addicting. Be kind to your mother, she is struggling w/cancer (or maybe trying not to face it) and she is an addict. You honestly cannot make her stop smoking, that is something she will have to take on herself. And yes, it will probably cause the cancer to come back.
This is really hard for you & everyone who loves her. After my brother was diagnosed, I was unable to stop myself from walking up to people smoking and telling them about my brother. This was my problem and I did finally stop myself (it took a few months). And nobody quit smoking because of my lectures (hard to believe,but true!). Addicts have to make the decision to quit. You cannot make the decision for them.
It is very hard for you right now & it will be very difficult in the next year or so as your mother starts down the road to recovery. Be kind to her and vent here

- Candace