It Never Ends

So there’s this girl. We used to be good friends. I told her all my secrets and such, and I even told her about my childhood, which wasn’t that awesome. But one day she decided she just didn’t want to be my friend anymore. She started bullying me on Snapchat and sending me mean things replying to my snapchats that very night after she excluded me from her friend group. She threatened to destroy my life if I continued to be friends with her best friend, Bri. She also threatened to tell all my secrets and my backstory to the whole grade, and possibly even the whole school. She turned all my friends against me and threatened to beat me up, and she even said once that when I died she would dance on my grave. On Valentine’s Day, we had a dance. Bri had decided she wanted to be friends with me instead of the other girl and didn’t want a friend that would control her life.. So things were finally starting to look up. Anyway, me, Bri, and my other friend Earl were all chilling and eating in the corner while laughing as music played, when the girl and her friends (which were also my friends) decided to walk over and ruin the whole day. Since Bri is a little overweight, the girl made a super rude remark: “Don’t eat too much, Bri!” I just rolled my eyes at that girl and said, “can’t you be nice one day of the year? It’s Valentines Day, for crying out loud.” And she said “And you’ll get beat up on Valentine’s Day if you keep talking!”
Earl then said “the better person is the first to walk away.” So me, Bri, and Earl got up and walked away, but SHE FOLLOWED US. Bri and her argued a few feet away while Earl and I talked about how stupid this all was, when I heard someone yell. I turned to see Bri crying and holding her eye, and the girl was throwing punches at her and shoving her to the ground. Teachers finally noticed and ran over to pull her off of Bri.
After that, I didn’t get to see Bri again for a couple months. Her mother pulled her from school and they moved out of my town. The girl who punched only got suspended for two days, and it was in-school suspension. She apologized to me over text, but when she noticed on one of my social medias that Bri had asked if I was friends with her again for any reason (I said no) the girl who punched got mad and threatened me again.. I’m still so upset, since this just happened about 20 minutes ago… I don’t know what to do. There are 9 weeks left of school, but she’s in my writing class, she’s twice my size, she’s amazing at sports, and she knows almost every single one of my secrets. Please help, all the advice I’ve found doesn’t help and I’ve tried going to the principal and the counselor. They haven’t done a very good job of keeping us away from each other like they said they would, since they moved the girl into a few of my classes…