Near the end of the book, Kit began planning to leave Wethersfield. She wanted to return to Barbados, understanding that her situation was different from before. She would have to work to sustain herself. Things changed one afternoon as she walked by the river. She suddenly realized that what she wanted was to be with Nat.

In the final scene of the book, when they have met on the wharf, Nat says that he wants to talk to her uncle, which is the first step in their marriage plans. Nat goes on to talk about someday building a house for them. Kit talks about having a garden that she and Hannah will work together. It is clear that she and Nat are planning a future together.

Well, it isn't spelled out explicitly, but it looks like she's going to be involved with Nat. He said he wanted to talk to her uncle, which in this culture means he's going to ask her to marry him.

She says she'll have a garden, and ideally Hannah Tupper will live a long time and teach her things. Beyond that, we don't know. Perhaps she'll teach school again?

We mainly know that she's found herself at the novel's end, and that Nat has found her.