Pearl is a different symbol of her sin, and a beautiful one at that.
In chapter 6, Hester's feelings about Pearl range from believing she should be in Eden (referring to the garden God created wherein everything was perfect) with the angels to being grieved, agonized, and terrorized by the devil-child that she becomes.
As Pearl ages she grows significantly more disobedient and Hester feels like Pearl works to point out the power of the letter on Hester's chest. She is particularly disobedient in front of other authorities and Hester feels tremendous guilt for bringing her into the world.
At the same time, when the authorities try to rule that Hester shouldn't be raising this child, that she isn't capable, Hester must at least love the child because the thought of them taking her child deeply hurts.