Personally i think diamond tiara bullies the cmc for a different reason that being maybe shes just jealous mostly because the cmc still have the potential to have a cutie mark that they can feel proud of while she cannot. When you think about diamond tiara the first thing that comes to mind is her cutie mark being a tiara and the fact that shes a stuck up b****, but what if her cutie mark reflected how stuck up and rude she is and often projects the jealousy onto the cmc because of their potential