But to be honest I think we're overanalysing a fluffy manga ^^
It’s only overanalysis in the sense that the way this series is written makes it unlikely that, once an issue is addressed, there would be some kind of further hidden psychological backstory needed to explain the characters’ actions. So once we got what amounts to Kase’s romantic “origin story” on the roof, that was to be taken at face value.
Now, there’s no compelling reason why it wouldn’t be theoretically possible to find out about, say, the first time Kase realized she was attracted to girls (it could be that semi-upskirt scene of the Delicious Plant Appointee bending over that we’ve seen, but it could have been earlier than that). Or we could get a bit more background on why Yamada is so extremely naive and sheltered (raised in hydroponic vats is as good an explanation as any so far).
Readers are free to have any reactions to Kase’s actions they like, of course, but in the story’s terms Hana-chan has been established as nearly as socially clueless as Yamada, only with an uninformed thirsty het streak, leading to unfortunate situations with strange guys that require Kase’s interventions.
Kase’s general antipathy to guys can be easily explained by those grotesque swirly things they have on their noses.