Hey, I went through something similar. I had a friend who was a very sweet person but was just so troubled and struggled very deeply his whole life with mental illness, and he took his own life horrifically. I have struggled with guilt over not being there for him as much as I possibly could have. I wish I understood the severity of the situation at the time and all the what ifs are overwhelming. One thing I’ve done that gave me some peace is having a mass said for him (he wasn’t really Christian either). I also have prayed a lot for his soul and truly believe he’s at peace. One thing your friend would not want you to do is torment yourself. You aren’t honoring her by focusing on guilt and pain. I recommend seeking some pastoral guidance or possibly therapy.