P.R.
It is a physical addiction as well as emotional. Nicotine is one of the most effective antianxiety drugs, that is why it is so addictive and hard to let go. It is more than will power. She will need to learn how to manage her stress and anxiety in a different way. Meditation, yoga, exercise. She can carry with her celery sticks or carrots when she is craving a cigarrete, they seem to help with cravings for some reason. She may fail one day and give in, tell her to start again right after she puts that cigarrete off. To take it day by day and slowly her body and mind will get used to being without.
It is a different process for everyone and she need to be kind with herself because she is making the right choice for herself. It can be done.
Good luck!