I get the feeling that we've reached a point in the series where Takashima-sensei has the luxury of writing for the tanks rather than for Wings specifically. If you've only read the fan translations here and haven't read the tanks, you've missed out on a crucial confession: Boys talking to Yamada makes Kase-san RILLY nervous. So her reaction to the celebrity gardener is within that context.
I think this is an interesting trend, because this is the first time in the "main" storyline, not counting specials, that we've gotten to hear Kase-san's internal monologue about her feelings towards Yamada. Between this and the lipstick chapter, I foresee the plot of the next several chapters (and ultimately the next tank) being about Kase-san's insecurities. Yamada is gonna meet some dude at the mixer, nothing is going to happen, you people are all going to lose your minds, and so will Kase-san before it's all straightened out in the final chapter.