It makes Brooke feel strange in her stomach. It is like the feeling when she reads a book like the one about the man with the bomb, or thinks a sentence, just any old sentence like: the girl ran across the park, and unless you add the describing word then the man or the girl are definitely not black, they are white, even though no one has mentioned white, like when you take the the out of a headline and people just assume it's there anyway. Though if it were a sentence about Brooke herself you'd have to add the equivalent describing word and that's how you'd know. The black girl ran across the park.