Yeah that's true, it doesn't help that the writer for both of them is the same person either (feel free to make some conclusions on that). Honestly if they made it clear that she was like this in the beginning I wouldn't be here complaining about it at all. In fact I'd say to anybody complaining: "Well what did you expect?".
The thing is that the way she acts contradicts her previous behavior so much it's like they are two different characters entirely. It's like in those moments you are warped into a porn universe. For example, at one moment you are studying in class then the next your (to your knowledge) normal teacher calls you into their office for "detention".
