If there are balls in the food menu, you may need to completely reset it to clear the problems you're seeing. Press the reset button on the back, then select reset from the download / reset menu on the screen. This will clear all gotchi points, purchased foods, purchased items, souvenirs, family information and history information, etc. Your Tamagotchi will go back to fresh-from-the-factory condition, but the problems you're seeing should be gone. Since this is your friend's Tamagotchi, you should explain this to them before doing it.
