One of the wives of the British soldiers who come to live with the Locktons, Sarah becomes "boss lady" (32.18) after Becky flees to New Jersey. She's pregnant, and this gives her a reason to defy Madam Lockton's orders that Isabel is not to go to the Tea Water Pump—that and the fact that all the other women are fighting over who isn't going to do the job. Sarah's "not a friendly sort" (32.18) according to Isabel, but she is at least even-tempered and isn't eager to punish people, unlike Madam Lockton.
What's really interesting about Sarah, though, is what she names her baby when he arrives: George. She claims to do this because "A name like George is a good one on either side of the ocean" (40.29). In other words, she's trying to cover all her bases so that no matter who wins the war, her son is named after the country's leader. Ha.
Earlier in the book, Curzon remarks that "Plenty of folks hereabouts haven't decided which side they favor. One day they cheer General Washington, the next day they toast the king" (6.48). In short, hypocrisy is alive and well, and whether she means to or not, Sarah echoes this truth.