Why is it alright for girls to hit guys ?

I was recently in the school year taunted and pushed around by a girl . My mom went to the school and reported many times she would stop for a while and start back up . I went to the principle myself even . One day she hit me , My mom who is a strong woman and gives me very good christian values . Told me to hit her back or push her . I have never hit a girl and feel it is not right . But one day i did after she had hit me in my head , and the principle called me to office and said why did i hit her ? And if i did gain i would be paddled and suspepened . But they did not do anything to her . Was it right for me to fight back ? And for the record i never did anything for her to star acting that way .