The only way she will ever quit is if she wants to quit. If she doesn't, don't bother trying to get her to. I quit cold turkey back in Christmas of '04. I was a 5 year, pack-a-day smoker so I know what I'm talking about.
What prompted me to quit is thinking about how I would feel if I did quit and get a handle on my drinking. Once I was a week into it I knew I mad the right decision, I never felt healthier. If one can make it through the first 3 days, then one can quit for good. It's those first 3 that are the hardest.
And as another poster said, it's all mental. If you can somehow get her to make the decision to quit then it can be done. All she has to do is make up her mind. Hope she does.