One of Pearl's major characteristics is her frequent unwillingness to go by any set of rules. Just the idea that something is forbidden or something is prescribed was always enough to throw her into a tantrum, she simply would not accept the idea of rules. Though Hester is slightly more pragmatic, she too is not always willing to abide by the rules that are set forth, particularly if they are contradictory or unfair.
Pearl also seems to have a violent disposition, or at least one that reacts violently to injustice. She is seen on several occasions demonstrating a rather serious temper, particularly when she considers the injustices of the town and the way that the children of the village elders can get away with things that most cannot.
But she is at times, in a way that contrasts much of her actions, willing to accept the idea of authority, shown particularly clearly when she forces Hester to pick up the scarlet letter and replace it in its place. In this way, Pearl is capricious and very unpredicable; it is in Pearl's nature to do exactly what it is she wants, but like Hester she is resolved to the existence of the scarlet letter, and the rules that bind her to it.