Hi, just to share my experience on solving bullies.
Sometimes we are able to find the bully from other girls though I, too find it rare that the bullies would be found. If the Bullies are found, we can use influence point to tell the Bullies to seize bullying.
Another way is to send the bullies or the bullied to a idol sister group. I solved it once using this method by putting a few other girls that the bullied is friend with together.
Cheers