Why did this have to happen?

She is insecure and her insecurities allow her to attack others in order for her to feel better about herself. Individuals who have a healthy level of self esteem do not attack others for no apparent reason. I would feel sorry for her she is obviously more than a little lost and insecure. Hopefully, she will grow out of this behavior. I would next time ask her, "does it make you feel better about yourself to treat others so rudely with such disrespect?"