I've been struggling with this too! I remember when it happened in a previous version i gave the bullied idol a LOT of contracts, to the point of neglecting everyone else - someone inevitably got mad at her, and when things escalated, I got the option to refer them to counseling and then find out that that person was bullying her. That hasn't worked so far in the new update though :( she used to be so popular and now she has no friends...