Here are a couple of points in addition to those mentioned above. Mercy worried about Kit telling stories to the children. She felt it was an indulgence. When Kit started to set up a small dramatic interpretion of The Good Samaritan with the children, Mercy protested, but Kit kept right on. When the Reverend Woodbridge dismissed both girls from their teaching positions, Kit tried to get him to keep Mercy on because it was not her fault or idea.
Later, in the meadow, Kit met Hannah Tupper for the first time. This was the beginning of their powerful friendship. As Kit spent time with Hannah and got to know her as a good person, she had to set aside her fears. Specifically, she had listened to what others had said to Hannah, labeling her a witch and a Quaker. Kit discovered that those labels did not match up to the actual person of Hannah Tupper. Kit had to set aside the gossip and prejudice that had come to her from others.
By the end of the chapter, Hannah had bolstered Kit so much that Kit resolved to go to the Reverend Woodbridge and ask for her job back. This was an action that she probably would not have taken before meeting Hannah.
In Chapter 9 of The Witch of Blackbird Pond, Kit is teaching school with Mercy. As a break from the rote memorization drill, they promise the children stories, and then move on to acting out the parable of the Good Samaritan. Just as the children get out of hand and start to really pound on each other (when acting out the mugging), Reverend Woodbridge comes in. The community disapproves of acting, and so he's very upset.
So is Kit. She runs away to the meadow to be alone. That's where she first meets Hannah Tupper. Kit gets so much support and understanding that she finds the strength to go talk to Mr. Kimberly, to ask for her teaching job back.