take turns to bring lunch. on your days, bring only healthy small servings. and if on her days she brings junk, try to like, make excuses that your teacher wants to see BOTH of you. and make a big detour round the school( good for exercise:P) and say, oh, i forgot! she only wants to see me! then your friend kate wouldn;t have time to go back to her locker for her lunchbox. then ask her to give it to you, and you dump it!:P