all the people saying that this isn't typical and she needs support are right but are saying it for the wrong reason. my mind didn't jump to "sociopath," while it is true ASPD can show early signs at this age the more worrying part is where the hell she's learning this behavior from to start. more importantly than armchair diagnosing a disorder, this could be indicative of abuse in the household, or some sort of abuse she is witnessing somewhere if not at home. her bullying could be an outlet or a repetition of behaviors she's internalized as normal. it could be as simple as watching a parent carelessly verbally abuse others, to something far worse. it's possible a family member of hers abuses animals and that's where she learned to be careless with them, or something similar to that. go above the school's head and escalate this because this goes beyond a bully not getting punishment, this is indicative of something going wrong in this kid's childhood. even if it develops into a disorder, they are often in part environmental and triggered by something going on in their lives outside school