Damn. Even though the whole thing was frustrating, it's the last page that makes it downright unrecoverable (as in, we'll have to ignore how shitty the characters were and move on, because no amount of plot can retroactively justify this).
I can imagine that Kase would want to avoid turning pretty much all of her friends against her at the same time by just telling them to shut up and that moving is her decision. I can also understand that she doesn't want to reveal her relationship with Yamada like this. And I would have trusted her to ignore the results of the race, and, if she loses, just tell them that she's not going to be bound by the unilateral bet because they didn't know how important that decision was to her.
Albeit it's not necessary, I would have been fine with that amount of drama, as it's making things awkward and uncomfortable but doesn't go against their plans or the established personality of Kase.
But her texting Yamada and telling her to delay just breaks that line of speculation completely. The delay would be completely unnecessary if she didn't actually consider cancelling the move, and that alone would already completely destroy any chance to progress the story if we couldn't just, you know, just pretend that it's okay (which is what I suspect will happen for the story to move forward). It also shows that Kase doesn't take the responsibility of moving very seriously, giving more importance to her friends getting all worked up than to life-changing plans. And finally, she'd rather do something that will undoubtedly hurt Yamada a lot than say no.
All in all, I feel like I can almost understand what the chapter tried to do, but a single panel throws the scale and proportions completely off. This is definitely not something you can read as a serious romance story, at this point, it's just the same stuff you'd typically see in high school romcoms.
inb4 it turns out we're starting a break-up arc because Yamada realizes that Kase just isn't that serious about their relationship.