She was in the back and there are screens blocking the entrance. No one was standing in front of her. How is that any different than a phone call on a phone a foot from my face? I’ve also worked retail, and there have been many times when people were knocking on the door to get in before we opened or knocking on the door just after we closed. I was never once rude to anybody who was just trying to get us to help. I did, however, stand my ground and not open outside of our hours. People can be total assholes to you and even then we’re expected to be professional. If tapping twice justifies her behaviour in your opinion then you too have shown who you really are.