From the time she was old enough to be aware, Pearl was fascinated with the letter on her mother's chest. The fascination was a concern for Heser at times because it seemed to afffect Pearl's attitude and behavior.
Pearl gets very upset when Hester removes the letter. Pearl's mother excuses her behavior because she understands that children cannot abide by change easily. The letter and Pearl are very much the same because the letter represents the blessing of having Pearl. Pearl is upset because she feels that her mother has removed a part of herself. It is symbolic of the separation between Pearl and Hester. The town sees the letter as representative of Hester's sin, however Pearl views the letter as part of herself--it is an embodiment of her.