Maybe she is a person with few friends, so he doesn't want his only friend to ignore him, so he doesn't want more people to get close to his friends. If you go out to play with that girl, you can take him with you, so that he won't feel lonely, unless you have something on your mind, or some privacy is inconvenient for him to know, or you can play with another person, unless that girl happens to be your best friend. Then at this time, you should accept her, because you have accepted your best friend, why can't you accept your best friend's best friend? In fact, in the eyes of others, this is a very naive thing. But maybe the girl didn't speak. As soon as she opens her mouth, she says that if you go out to play, take her. Actually, you can try to go out to play a few times first, and you can take her with you. Unless she refuses you several times, you can not take her out to play in the future, that's all.