Is etiquette officially disappearing from the society?

No they don't and you should have spoken to her manager about retraining her in customer service. Let him know that if something is not done, you will be writing a letter to the newspaper about the poor management of that particular establishment! Too many people just "let it slide" so idiots like that can get away with their disrespectful attitude. Not me. I work in customer service and would never say something like that to a customer. Sorry for your bad experience!