Kit was a lost but hopeful orphan at the beginning of the story. She was coming to this strange place to see family she'd never met. At the end of the story, she has family, and more than one family (if we assume she'll marry Nat). She knows who she is, and respects the land she's come to.
Mercy went through an illness, but her main change is that it had looked like she might be a stay at home family member her whole life, due to her illness, but she and John are now in love and to be married.
Judith was very proud and off-putting at the book's start. She is somewhat warmer as a person now that she and William are together and happy, and she has a house of her own to plan.