I got bullied then beat up by a girl?

we are both 15. she was calling me names and making fun of my weight, so i told her to leave me alone and then she go right in my face screaming at me so i pushed her away, and she got very mad, then ran at me and pushed me to the ground. then as i was getting up she kicked me in the gut then hooked my face and i fell down, and as i was down she kep't kicking me very hard until i was crying. then she sat on me and grabbed my arm and twisted it and told me that next time she sees me i will be put in the hospital, then she let go and stomped on my gut, then walked away laughing. im very scared, what should i do?