After rereading the classroom scene, I’m even more convinced that the classmates who were prejudiced against Mitsuki were just reaching for any excuse to exclude her from participating in the cafe.
First they attacked her for not openly backing the maid cafe idea. She may have been spaced out for much of the discussion but so what? Are only the people who expressed excessive enthusiasm from the start allowed to volunteer to take on a lot of the work, even when they are the only one with any actual experience?
Then there was the part about dressing as a maid. Keep in mind, the outfits have not been purchased yet. First, they implied she wouldn’t be okay if she had to wear a maid outfit, then when she claimed she would be, they switched tunes and started shaming her for wanting to wear the maid outfit. I can forgive Yano for not keeping with what they were saying, because they are constantly moving the goalposts.
They were just on her case for not openly backing the maid cafe idea, and now they are framing her as being too enthusiastic about wearing a maid outfit. But the class by majority, I assume, decided on wearing the maid outfits, and I doubt they could get many girls to sign up to be maids if the outfits were particularly lewd or revealing. And of course, as we saw with the Cafe Liebe summer uniforms, even if the outfit does look different with Mitsuki‘s figure, there are simple ways to address that without messing with the aesthetic too much.
That’s not the point though, they created a no-win scenario when they asked Mitsuki if she would be okay with wearing the maid outfit. If she expressed anything other than willingness to wear it, they would have pressured her to not be part of the wait staff in favour of people who are actually willing. Because she said she wanted to, they twisted her agreement to mean some shameful desire.
Mitsuki‘s not really good with following subtext and recognising when someone isn’t being honest with their intentions, so she likely didn’t understand that she was being unfairly bullied out of participating and none of the arguments had any actual substance to them. That’s why she fixated on the idea that Nakamura only spoke up for her because he had feelings for her. The class just used his feelings to claim he was biased and had ulterior motives to dismiss him outright, but Yano takes things at face value, and it was the only part she seemed able to grasp.
Of course, Hime is only told the version of events as Mitsuki can understand them, so she’s naturally just confused. Had she been there, she would have seen through the half-assed excuses for what they were and called them out on it.