I guess Koiwai is being pretty honest here; Hinaki and Shunsuke could have eventually fought like this over something else. Shunsuke's starting to spend time with someone else, and Hinaki no longer knows if she likes this new Shunsuke. Is this correct thinking? I don't think so. I mean after all, Shunsuke's only spending time in the library like that to help with Kowai's writing.
But I do think that Hinaki isn't sure if she loves Shunsuke yet. She thinks he's a good friend, but he's now changed considerably. He no longer acts the same with her. So does she still want him to be her best friend? She doesn't know.
I feel sorry for Isuzu though. She's been ridiculed all her life for her dreams, it seems. I hope Hinaki's able to help her overcome that.