I do not know what regulations are about this, but they should not apply to childrens who want some money for their vacation. Selling lemonade for a child is so common that you even see it in movies and animation movies. Although, selling it at 50p seems a little bit incorrect but if there are clients who wish to spend that amount of money on a lemonade, than why blame the girl. I remember myself beeing a child and beeing in need of money for vacation. Other kids do not have the initiative to do something like this and they ask for money to their parents so I believe she should be only educated and not harassed and shut down.