What does Hester realize while she is standing by the scaffold during the sermon in chapter 22?

Hester takes Pearl and goes to stand near the foot of the scaffold in order to listen to Dimmesdale's speech. Pearl then takes off and runs around playing. The ship's captain gets Pearl to come to him, and he gives her a message. Pearl returns to her mother and tells her that Chillingworth has told the captain that he will make sure Dimmesdale gets on board, and that Hester only has to worry about herself and Pearl.Hester is crushed by this new information.