Girls Use Indirect Agression to Manipulate and Shame Competition.

    While it's that boys do tend to be more direct with their aggression, girls on the other end, learn through their verbal skills how to manipulate people, form groups in order to pressure or shame others.  Boys do tend to bully but girls are the ones who use the most peer pressure, and peer group in order to bully each other:

This was found in a study titled, "Do Girls Manipulate and Boys Fight?", where they have revealed that girls as young as 8, tend to use indirect means of aggression; such as passive-aggressiveness, manipulation and using groups to intimidate rivals. While not prevalent to girls of that age, the trend and frequency skyrocketed by ages 11 through 15 - which the study also revealed that adult women were the biggest users of indirect aggression:

  

And from another study title, "Do human females use indirect aggression as an intrasexual competition strategy?" women have been found to use the same types of passive aggressive strategies in order to exaggerate their own sexual value by shaming or defaming another women to other women, or the men they  target for sexual selection:

"Indirect aggression includes behaviours such as criticizing a competitor's appearance, spreading rumours about a person's sexual behaviour and social exclusion. Human females have a particular proclivity for using indirect aggression, which is typically directed at other females, especially attractive and sexually available females, in the context of intrasexual competition for mates. Indirect aggression is an effective intrasexual competition strategy. It is associated with a diminished willingness to compete on the part of victims and with greater dating and sexual behaviour among those who perpetrate the aggression."