Rejection.

Marinette isn't good enough. Not for her friends, not for Chat, not for Adrien, and most definitely not for Paris. Unhealthy coping mechanisms, like cutting seem to do the trick. A worried cat stops by and well just read the fuckin book I'm not good at this.
TRIGGER WARNING- mentions of self harm and depression and like all that stuff so please don't read this if you're not comfortable with that