What behaviors will make you feel that the other person is polite?

Once on a bus, I saw a girl sitting in the front row, wearing a hat and headphones listening to music. Later, an elderly couple came over. It happened that there was a seat next to the girl. Grandma sat on it and grandpa stood beside her. The girl waited for a stop or two, then took off her headphones and hat and said nothing. The crowd behind her squeezed into the door and stood for nearly six or seven stops. Grandpa sat in that position because he was near. Later, the girl was also very polite. When others want to get off, she will take the initiative to avoid it. I feel that the girl didn't tell the old man directly that I gave you my seat, but quietly gave her seat, giving her some self-esteem while ensuring that the other person would sit in the position. After such analysis, I feel that this girl is really careful and polite?