Kit considers marrying William so she can fit in, because he is rich.
William Ashby was originally interested in Judith, Kit’s cousin. However, when Kit comes to town he seems to become interested in her instead. For Kit, he is certainly the practical choice. She can marry him and be respectable, and do just what the Puritan colonists want her to do and be what they want her to be. She does not see much in William though. He is not friendly or passionate, and the two could not really be more unalike.
Kit describes William as “sturdy” (Ch. 5). She is not smitten with him. Judith, however, is. She is frustrated with Kit because William switches his affections to her.
Who hasn't heard that his father has three acres of the best land set aside, and the trees all marked to build the house the moment Master William makes up his mind' And he was just about to make it up, too, when you came along." (Ch. 6)
This of course, is reason enough to marry him. He can build Kit a house and they can live comfortably. She can fit in, for once, amongst the other colonists. After all, he likes her, doesn’t he? She can grow to like him. He is dependable. He will be good to her.
The biggest problem with William is that he is not much of a talker. Their visits are a bit awkward. He just sort of stares at her for a very long time. The only time William does ever speak up is in mixed company, to talk politics. His politics sort of agree with hers. She is in favor of the king, and he does not think the colonists can fight the king. It is not exactly the same thing, but it more or less puts them on the same side. Kit like the fact that William stands up to her uncle.
Kit seems to enjoy the attention too, because everyone wants William.
It was flattering, she had to admit. The most eligible bachelor in Wethersfield and handsome, actually, in his substantial way. Sometimes, as she sat knitting, aware that William's eyes were on her face, she felt her breath tightening in a way that was strange and not unpleasant. (Ch. 7)
In the end, however, Kit realizes that she cannot marry William. First of all, for all her bluster, Judith is the one who is really in love with him. Second of all, Kit is really in love with someone else. Nat is more Kit, and what they feel for each other starts out as friendship and grows to true passion.
Kit’s story is a good example of why you should not settle for just what society wants from you. If she had married William, it would not have been fair to either of them. She was not right for him. She would have been trapped in that life. She needs someone who understands her, and he does not. Nat does, and with him, she can learn to fit in but is still free to be herself.