This GIRL on my nerves!?

I have tried everything! this girl will nto leave me alone........about a week ago this girl me and 2 of our friends were all playing around on messenger. one of them is dating me frined and he and his best friend was saying stuff to this girl like she was y and crud and mainly playing around wih ther the other guy likes this girl a little i think and he said a lot of other stuff...the next day at school shes spreading around the hole school that they said she was y which embarrased them. and since i like my est frineds boyfrind..his best frined i like and she knows it and even he knows it bragging that he said that which lead to a hole big fight and tonight she said i need to get a life and that he doesnt like me...well i mean i knwo he dont like me, were like good frineds and since she keeps telling him bad things im doing ..she dont tell him that sutff shes doing too...i need ur help to know wat to do to move on and forget her!..skewl is 1 thing but plz help me im 13, need u!!