I need a quote in the book about this question Why did the main character decide to confront the antagonist in chapter 9? What motivated them?

From the text:

“I’m not mad. I’m worried about you.” But that’s only half-true. I am mad—furious, in fact. All this time I’ve been blindly coasting along, the idiot sidekick, thinking about our last real summer together, stressing about the matches I’ll get and evaluations and boards and normal stuff and she’s been nodding and smiling and saying, “Uh-huh, yeah, me too,” and “I’m sure things will be fine,” and meanwhile, behind my back, she’s been turning into someone I don’t know—someone with secrets and weird habits and opinions about things we’re not even supposed to think about. Now I know why I was so startled on Evaluation Day, when she turned back to whisper to me, eyes huge and glowing. It was like she had dropped away for a second—my best friend, my only real friend—and in her place was a stranger.

That’s what’s been happening all this time: Hana has been morphing into a stranger.