I work with a woman who I have become really good friends with, we started around the same time last year and hang out outside of work frequently, go to the gym together after work etc. Recently she has been having some performance issues and has made some mistakes, I have always done my best to help and point out things but sometimes it seems she doesn't listen. Recently I have noticed something that goes against our procedures that has happened on several occasions, I have pointed it out to her to try and explain why it isn't correct. My colleague also noticed this and ultimately I felt as though I had no choice but to inform my manager. She will speak to her and I am terrified. I feel so incredibly guilty and uncomfortable because I don't want to get her into trouble and I know that she is having a hard time in her personal life. It will also look extremely obvious that it was me that said something as I brought up the same thing with her. I want to give her the heads up but I obviously can't do that as it would be extremely unprofessional! Does anybody have any advice?