My Friend is Suicidal?

Ok So My best friend I've know for 10 years (we 13 now) almost committed suicide. I knew she was cutting but i did not know how long cause she just recently told me (and NO she is not lying I saw the cuts) And someone posted on facebook (IDK who) about her suicidal thoughts(that she almost did suicide) and the cops and CPS came to her house. I did not know She was suicidal, thank God the person posted that on facebook or she would be gone:/. What Im asking is how can I make sure she does not commit suicide? and that she stops cutting?