Can you tell me how to help my cousin with her cell phone addiction?

Well, mostly you: Can't. People have to recognize that they have a problem and decide to deal with it. Family members can help sometimes, but often are confronted with anger, resentment and denial. Members of her immediate family may be in a better position to help, and may need to stage an intervention if her cell phone use has truly started to interfere with her life. A mental health agency should be contacted.