Chapter 6 ofThe Scarlet Letterfirst describes Pearl as a character and as a catalyst of change in Hester's life.
Pearl is meant to serve a role in the novel, and the term "elf" responds to the possibility that, since she is a child born out of "the luxuriance of a guilty passion", the sins of Hester and Dimmesdale have somewhat permeated Pearl's existence giving it an air of evil.
Even Hester admits that naming her "Pearl" had nothing to do with the girl's looks, but with the high price that she has to pay in order to co-exist with her.
However, it is in chapter 8 where Hawthorne refers to Pearl as an "elf", due to the behavior that Pearl displays in the Governor's Hall.
The aldermen basically tell Hester that they are considering the removal of Peal from her guardianship. After all, Hester is thought to be a bad example to the entire settlement. Hester, displays every sign of rebellion as she pleads her cause, and she even demands that Dimmesdale, as a well-respected leader, pleads on her behalf as well.
Hester asks them to examine Pearl as a way to show them that she is fine. However, Pearl shows that she is, indeed, a bit wild in her reactions.
The old minister seated himself in an arm-chair, and made an effort to draw Pearl betwixt his knees. But the child, unaccustomed to the touch or familiarity of any but her mother, escaped through the open window and stood on the upper step, looking like a wild, tropical bird, of rich plumage, ready to take flight into the upper air.
Most of all, she seems to be omniscient, that is, she has a form of knowledge that looks as if she could "read" the intentions of the people who surround her. For this reasons, we find Pearl acting in a passive-aggressive way (pushing buttons) and making everybody react at her odd behaviors. An example in this chapter occurs when Pearl is "tested" in her Catechism by being asked who "made" her. Instead of outright saying that God made her, Pearl has a strange way of answering.
After putting her finger in her mouth, with many ungracious refusals to answer good Mr. Wilson's question, the child finally announced that she had not been made at all, but had been plucked by her mother off the bush of wild roses, that grew by the prison-door.
It is by the mercy of Dimmesdale that Hester is finally left alone. However, the impression that Pearl leaves, as an elfin (a creature that is strange, supernatural, and mischievous) is quite evident.
"A strange child!” remarked old Roger Chillingworth. “It is easy to see the mother's part in her. Would it be beyond a philosopher's research, think ye, gentlemen, to analyse that child's nature, and, from it make and mould, to give a shrewd guess at the father?
Hence, it is left to the reader to wonder if there is any element of the supernatural in Pearl. However, we know that if there is any, it all goes away during her adulthood, since Pearl actually marries well and leads a good and normal life. Hence, it is perhaps the guilt and the secrecy of Hester and Dimmesdale what seems to bring in the uneasiness of Pearl's existence.