Your analogy is apt! It's true that Kana comes across as enigmatic and sharp tongue sometimes. But I think she's a little bit dangerous, especially when the main character suddenly fainted and woke up to See Kana's face, which was kind of creepy. There's a feeling she might have something to do with the disaster at the school (not sure).
Will Haruka become yandere? I think Haruka already has too many attributes, such as domestic violence, childhood sweetheart, and dynamic girl. And does she have a tendency to be yandere? Maybe it's because everyone has changed a little bit by that point in the plot? But I think Haruka's relationship with the protagonist is so deep that she may not be able to accept that the protagonist falls in love with someone else, so she may go crazy (her own experience is also tragic). So maybe lol.