How can I get my girlfriend to quit smoking?

Even if you have expressed that you don't like when your girlfriend smokes, she is able to make her own decisions, and smoking cigarettes is one of them. I can understand why you would want her to stop before she becomes a habitual smoker, but the only thing that will make someone quit smoking is when they actually WANT to quit and are SELF-motivated to quit. This has been my observation, at least.

I am a smoker, and I have quit a few times - it didn't last for long on each occassion, but when I am ready to quit entirely, I will. People telling me I shouldn't smoke does not compel me to stop. When a smoker quits, it's because he or she has made the conscious decision to do so, and outside influence may play a part in this decision forming, but outside influence alone will likely not be enough.

If you're polite, you can't do that. It's her own choice to smoke.

Otherwise, you could say, 'If you don't stop smoking, I will not kiss you anymore'. Well this one would be very rude. So I would say, be polite, and let her smoke. Either, she would smoke in secret anyway when she feels the urge to smoke.