Imagine if Madam Bustier had quietly told her students that Lila had a lying disease? She doesn’t think Lila would ever deliberately hurt someone, still thinks the best of the girl, but since this lead to her class president getting expelled she figures she should tell her students in case Lila accidentally lies and hurts someone. So she tells them and admonishes them not to spread it around, but she doesn’t tell Chloe or Sabrina, because she might be a bad source of life advice but even she can recognize that Chole doesn’t need the ammo.
The class all decide to treat Lila as a normal student. So they don’t tell Lila they know, and Madame Bustier forgets to. So Lila doesn’t know.
Marinette isn’t happy about this; she doesn’t believe Lila can’t help it and she’s still worried about what she’ll do, but she decides to keep quiet for now. She has no idea how to prove Lila’s lying deliberately and her friends are still her friends and not blindly following Lila, so she deals with it. Adrien of course sticks with this story, and tells Marinette of the deal he made. Together they keep an eye on the situation, wary of what will happen when Lila figures it out.Â
Meanwhile without knowing it, Lila’s fangs have been pulled. The class still listens to her, but they don’t hang on her every word, and though they’re still helpful, they don’t carry her bags around everywhere. They don’t believe her more farflung stories, but they don’t mistrust her with their things or siblings. For a while, it’s effectively a stalemate.
And then Lila finds out and she is PISSED. Either her rage pushes her into visibly bullying or lashing out at Marinette which eventually leads to a proper downfall, or she’s simply rendered impotent until the next time she moves.
