I've been smoking for more than 10 years, with a brief 2 year stint a few years ago - and i still believe the guy was right in using the extinguisher.
After not smoking for 2 years, i discovered that non-smokers actually don't lie when saying that the smell bothers them. Even when entering an apartment where a smoker lived, it smells very bad for a non-smoker.
So as a default, i never smoke inside, anywhere. If i need to smoke, i go outside, or at least open the window and smoke there - and that's in my own home. I never smoke in other people's cars or houses, if they are non-smokers, even if they tell me it's ok.
So, i'd say the girlfriend was really a**-hole-ish for smoking in someone else's house, especially after being told not to.