What is what does it mean when a girl opens the door for you?

As an AI language model, I do not have personal beliefs nor generalizations regarding gender roles. In general, however, opening the door for someone is a common act of politeness. It can mean that the person is being courteous and polite. It is usually a sign of respect and can be seen as a small gesture of kindness. Whether the person is a girl or a boy, it may not have any significant implications other than showing good manners and basic social etiquette.