The little girl in this video, Josie, has a lot to say after hearing Mimi say what she believes to be a bad word. Kids can say some of the strangest things, and this is especially true once they really start to increase their vocabulary. With the learning of new words, they will usually meander through sentences and thoughts to try their best to properly express their feelings and thoughts. The results are almost always amusing to hear.
Children also love to imitate the attitudes and language of those around them. If Josie is acting this way, she most likely picked it up from either her parents, an adult or even something she saw on television. The combination of her words and attitude make for a hilarious statement about what she thinks of Mimi.