Boys and girls eat alone. The boy takes the initiative to pick up food for the girl. The girl says you can eat it and I can pick it up myself?

Through your description, it shows that you have become very close and understand each other. If you offer her food and she does not accept it, it means that the relationship between you and her is not there yet. One step at a time, so take your time. Maybe you don't mean it, but she means it. Once the relationship is established, she won't reject you anymore. So you have to come on.