One of the things that makes quitting hard are the daily triggers. Smoking is a habitual thing. For me, I had a pattern. If I got in my car, I lit up. If I finished a meal, I lit up. So on and so forth. If you work a daily 9 to 5 or so,me other thing with a standard schedule, you face the triggers all day long.
So picking the right time to quit is an important part of the process. For example, if you have a long weekend coming up, smoke your last cigarette the night before and plan a weekend activity that distracts you from all those routines that trigger you.
Here is an important fact about quitting. Willpower has not a damn thing to do with it. You will fail. There are a lucky few who don't but they are exceptions and as inspirational as they think they are, their experience does not represent typical results. You will fail. You cannot beat yourself up if you do. You must recognize that your addiction is part chemical, part psychological, and part habitual, and your addiction is working hard to beat you in your goal. Your body wants the cigarette. You must solicit the support of your friends and family and you must try again.
Over the long haul, if you are serious about quitting and you keep focused on the goal, there will come an attempt that will not fail. Might be your second try, might be your twenty-second try, but persistence will pay off.
Also, Zyban (which is the same as the generic Wellbutrin) worked for me. Results vary. It is a drug used in the treatment of depression but for many it curbs the effects of withdrawal. It isn't for everyone and in a few cases, the treatment is worse than the problem. But more than enough people are helped by it for me to say it is worth it that you (or, she) talk to your doctor about it.
If you choose to use Wellbutrin, you'll start taking the drug two weeks before you quit. Then, you quit. Then you get through that rough first part. Then many screw up and think, "hey I feel great", and quit taking the drug. Don't. Stay on the drug for the full period of time (typically three months) that your doctor suggests. Otherwise, your risk of relapse is higher.
Quitting is one of the hardest things anyone can do. Good luck to your girlfriend. I hope she kicks it for good, but if she fails, she should remember that it is normal and try again. She'll get there if she really wants to.