B She still didn’t know why she said it, but it led both of them to say a lot of painful things.
C If you are, too, let’s go up to my room and look at pictures.
D Kendall sighed with relief.
The best sentence that supports the theme "People can disagree with and still care about one another" is C: "If you are, too, let’s go up to my room and look at pictures." This sentence highlights Flora's willingness to move past their disagreement and reconnect, indicating that despite their conflicts, their friendship remains important to both of them.