I lost my best friend for life.?

well. i've had this one best friend since i was 5 and now i'm 14. we grew up to grade 6. and i ditched her because i thought she changed. SHE IS SUCH AN UNDERSTALBE AND TRUSTWORTHY BEST FRIEND. and now. i miss her. because we left school. and. i miss her. im not telling the whole thing, im cutting the swtory short but we were the bestest friend ever. everyone at school agreed and now i regret losing her and i want to be best friends again but... we dont go to the same school anymore so what can i do? im writing a letter to her but thats not enough, pleadee help im depsrate. im about to die inside