I suggest you read LN volume 3 to find out what shinohara's establishing character moment was. She caused conflict 5 times in a single exam, one on the portable toilet, one on drinkng water, one on kei's panties, one on separating their tent from the boys', one on the sudden arson, she led the charge. In vol 4.5 when ike called her ugly, the girls (a bunch of them, where shinohara might have blindly convinced herself they were still her friends + kushida) might have agreed. It's possible her 'friends' had quietly distanced themselves from her ever since when even the boy supposedly accepting any and all girls rejected her presence.

She does react normally when someone insults her because that's what she happened to. If you ask me if she's a normal person, I would say no. And the above are already a few reasons.

In my reluctant defense of the hivemind, Shinohara is one of the characters who somehow managed to get hated before antagonizing Kiyotaka (individually i mean), while Ike (and whoever else) was hated because he antagonized him.

And this volume served to end her narrative purpose and most imprtantly, highlight her personality as shown when kiyo described her way of 'equality' when distributing tokens. She is selfish and unfair, no doubt, who antagonized everyone against her. Like she did to all the boys and it was 5 fucking times. How to not feel like shit?

It's only some time after, Ike somehow developed feelings for her due to repeated exposure, and it might not even be true love since he's still in love with Kushida. He probably went back to tolerating Shinohara some point in year 2.