The theory of Pearls being servants has been confirmed, which may explain multiple things. Since Pearls are treated like dirt, and Pearl was once a servant like the others, this could explain her lack of self-confidence. She has probably been told she is worthless and been laughed at which would make her feel small and insignificant. However, her attitude towards humans is a bit odd considering she once was treated like nothing. She almost seems as if she is convincing herself that she is not nothing and that humans are.