how to help my little sister dealing with self harm

ive delt with wanting to hurt myself before but ive never actually done it.

my little sis (11 years old) it cutting herself on purpose.i dont know how to approach talking to her about it and im worried about her. for the last few days ive cried a lot for her cause i cant imagin what shes going through.i really dont know what else to write. PLEASE HELP MEEEEE!