The consultant behind the counter has a disgusting attitude towards clients . For personal reasons, the order was not canceled immediately, it was delivered to the point and they came to refuse. After that, the child (sent to refuse the product) listened to a lecture on why to do this and order at all. I don't understand such a moment, this is your job that you are doing, I'm sorry in advance that you were distracted from more important things. I hope they will at least have a conversation with you about how to communicate with clients and children (if you are not satisfied with something, tell the parent, and not run into the child.)
Have a conversation about the ethics of communicating with customers. If "she" continues to make remarks with a haughty expression, then there will obviously be no more visitors. Work on it, there has been more than one similar comment.