The female has been brainwashed to hate and to compete with each other to garnish the male's attention. Even when the female is alone without the male gender being in proximity, the behavior is still prominent because it is believed to be necessary for self-preservation. It is said that the male gender is competitive but the female gender takes the reign on the trophy, the belief that they must be better than each other is so very prominent. And the source is because the female has been programmed to believe they must compete with each other to attract the "best" male but in the process she forgot her own worth.
What they do not understand is the supposed worth that they believe they have is determined by a flawed and ego based system given to them by the male gender. It is a system that will always leave them feeling worthless and abused. The start of ending the destructive cycle is the female’s awakening and awareness of her worth outside of the male’s expectations.