Tobacco and vinegar will just make her take up smoking and salt n vinegar chips... Haha. Kidding. Habits are conditioned, so make a conditioning for the condition. Have her wear a rubber band and every time she goes to chew, tell her to snap it. It'll hurt, make you laugh, and maybe hurt enough to detour her from doing it again and again. Or it might give her an insatiable desire for pain. Who knows, addicts will be addicts.