To be clear, I’m anti-Mirika, but no matter which camp you’re in, this chapter should make you like her more, not less.
Mirika expects that she’s going to lose, and is trying her best on the 1% chance that she’ll win. She hears that the other girls would be displeased if she was rejected, and she doesn’t want to ruin their happiness without even getting Naoya for herself (because she thinks she WILL be rejected).
So, she comes up to them and acts like a colossal bitch, plus assuring them that she’ll be OK even if she gets rejected, because she’s the Mirika and doesn’t even care that much (obvious lie.)
All her bitchiness in this chapter is just to convince the other girls to not feel bad after she loses.
Mirika is no saint, and I still don’t like her, but it’s not like this is her real personality or how she actually feels.