Raina's flashback to learning her dad is about to be laid off. It's so out of nowhere since, at this point in the book, Sisters has been more lighthearted than Smile. The panel where Denis tells them he only has a few more days is completely black with only his face and the speech bubble showing.
Then young Raina goes through a sort of dreamlike sequence where she wishes that she hadn't just gotten a new baby brother which took all of their mother's attention, or the sister she'd begged for for more than a year, believing that her own flesh and blood hates her. The entire family hugs just as the sequence ends.
Raina and Amara watch their parents talk about all of the financial problems they'll face before Denis finds another job. At this point, Raina is 8 years old and Amara is only three. That's far too young to be worrying about something this serious.
Actually, Raina tries and fails to connect with literally everyone at the family reunion: the adults are too angry and fractious, fighting over every little thing (hinting at the relationship that Raina and Amara could've had if they hadn't reconciled as children); the other teenagers, as stated above, don't seem to think much of her; and the kids are too rowdy for a fourteen year old girl to play with. Distraught and lonely, Raina walks outside ... to see her sister sitting on the steps.
Raina: You ever feel like you just don't fit in? Amara: All the time. The difference between you and me is, I don't care.
Raina admits that she actually did have coloring pencils and offers to give them to Amara. Amara refuses, saying she doesn't care about socializing. Raina then blows up at her sister, telling her that she won't do anything nice for her again. Amara's response:
Amara: You're not being nice. You're just feeling sorry for yourself. Raina: That's not fair! Amara: But it's true! If Lindsay(our older cousin) wanted to hang out, you'd be gone in a snap! Raina: I'M GOING ANYWAY! Amara: SO HERE YOU GO! [SLAM!]
That night, Raina realizes that the cousin she always wanted to be her sister doesn't think of her the same way and that the sister she actually has hates her and everyone else. That's not something pleasant for anyone to realize, especially someone like Raina, who has a pretty miserable school life due to her insecurities and bad friends on top of her problems at home.
The ending. Raina finally realizes that her parents haven't gotten along for ages, and that she's been absent in her family due to always retreating into her Walkman whenever things go awry. In real life, their parents did get a divorce... five years after Sisters is set. They're good friendsaccording to Raina, but in the context of this story, it's pretty depressing to realize that your mom and dad aren't as perfect as you think they are.
The sadness doubles when you realize that Amara doesn't use her Walkman as much as Raina uses her own, and thus has picked up on her mom and dad's failing marriage. How many more arguments has she seen, or even caused, due to spending more time with her family than her sister?