Susan writes to Juliet and admits that because Sidney leaves her letters on his desk, she reads them. She wants to assure Juliet that Billee Bee isn't running errands and sending things because Sidney asked her to—she's disgustingly devoted to Sidney and sends things of her own volition. She's also from a temp agency but has somehow made herself permanent.
As far as Susan is concerned, Billee Bee must have ulterior motives given how devoted she is to Sidney. This suggests that not all chosen family is positive, especially given that the reader has thus far been given no reasons to question Susan's assessments.
Isola writes Sidney to thank him for the book on phrenology. She says she's been studying hard and is thrilled to learn so much about her neighbors. Eben is "garrulous," and Juliet has a lot of "amativeness" and "conjugal love." Isola's surprised Juliet isn't married with a reading like that. Will made a joke about Sidney when Isola shared that with the group, but Isola kept Sidney's secret. Dawsey escaped before Isola could read his head. She finds him perplexing. He was chatty for a while but is silent now.
Dawsey's escape after Isola's reading of Juliet's head could easily point to the fact that Dawsey is actually in love with Juliet, though it seems as though nobody on Guernsey picks up on this. This suggests that at this point, they're telling their own stories about the relationships between members and aren't willing to think critically about the information in front of them.