Huh!? Did I miss something here?
I could understand her with a random guy etc but for her to accept and go with the one guy she has so much disdain for, consistently calling him "fake prince" glaring at him, yet one random present he has for someone else makes her choose him. I know it is clear he said something that can be used against her or maybe offered to help Kumagaya get more involved into the class.
Think Author should have wrote a chapter before this showing the fake prince and her getting a tad closer or something.