My best friend is dying, what do i do ?

hii. well here's the story. my best friend, has kidney lupus. she has recently gotten new pills which means she doesn't have very much time left. she was diagnosed in 5th grade. the past family members who have had lupus only lived for 2 years with it, we're in 7th grade. im so scared. a friend of mine, aleyris has recently died and our whole community was depressed. and i cant imagine what her best friends went through. in the end, im scared shitless. i don't know how im going to survive without her by my side. shes like my sister. so please help. what should i do when shes gone ??