i'm sorry. you couldn't have known, you couldn't have stopped her. if she had wanted you to know, she could have told you. it's just very hard because if you are suicidal and tell people, everyone just says "oh, she's just looking for attention," and no one gives a fuck... So either people think you are desperate for attention, or you do it and people think "if only they had said something." It's really a catch-22. So a lot of people don't talk about it. I'm not saying you would have said she was searching for attention, but a lot of people who are suicidal have had that experience -- even on this board -- and so they choose to keep quiet. but you couldn't have known. don't feel guilty. she wouldn't want you to feel that way.
Another thing, also... I think it is difficult for non-suicidal people to understand what it feels like to be suicidal. This has been my experience with extreme depression: Even if you have a lot of great stuff going on in your life, everything hurts. It's almost like physical pain. All your energy is gone, it's hard to even move your head, you can see things, but you don't really see them. In the same way that alcohol changes people's perceptions, extreme depression really changes people's perceptions, altering their entire world and coloring the world in a completely different way. When you are suicidal, it's really hard to reach out, because when you are suicidal, often you don't want help. You just want to die, in the same way you want to eat, or want to have sex. I am saying "you," but I really should be saying I. This has been my experience. When I'm suicidal, it's often hard for me to walk or even to breathe. It hurts behind my eyes, but I don't cry. I can barely eat, I don't want to pick up the papers on the floor, I just want to dissolve. I'm trying to get better, but trying to get better is really difficult, because deep down, I know that even if I get better, I will probably relapse at some point. If I stay alive, this is going to be a long, difficult fight. Also, personally, when I am suicidal, I feel extremely guilty, worried about how the people I care about will react if I do end up dying. Part of me doesn't want to even mention my feelings to them, because if I do, then if I actually do kill myself one of these days, my friends will say "I knew my friend was suicidal, and I still couldn't do anything! Why didn't I do more?" If you don't tell anyone about how you feel, you can feel less guilty. Another part of my experience with being suicidal is that I intentionally try to shut people out of my life -- because I don't want to involve more people in my misery. When I don't have anything happy to say, and I'm constantly in pain, I feel like a giant leech when I talk to people. I always just talk about myself and how sad I am, just sucking on their energy and making them feel annoyed and sad. And even when they try to hide it, I know how concerned and annoyed and confused they are. And these feelings end up becoming the substance of friendships. So, I try to keep things to myself, confiding in my pschiatrist and a few close friends who I think really want to listen, even if I do end up dead. But sometimes it's even hard to talk to those people.
I guess my point is that when I've been suicidal, my worst fears were that if I did ever kill myself, the people I care about wouldn't be able to deal with my suicide. I think most suicidal people are probably silent by choice, because they don't want to be a burden. Sometimes, I think there are some suicidal people who are really isolated and don't have anyone to talk with. But I think there are a lot of people, like me, who don't want to involve other people when they feel this way. Sometimes I look at myself a someone with a huge bomb strapped to my back that might never go off, but could go off at any second. I just want to stay as far away as I can from other people.
People don't view severe depression in the same way as cancer, because you can't do a biopsy on depression, and people with depression can still walk and talk. So, people view those with depression as seeking attention and lazy and somehow flawed. But when you have severe depression, it really is like cancer -- because some people survive, and some people don't. And for some, it is debilitating. But when people die because of severe depression, the people left behind somehow blame themselves, but they really shouldn't. You wouldn't feel guilty if your friend died from breast cancer. You aren't a psychitrist. You had know way of getting inside her head and physically altering her brain.
If I ever do commit suicide, I would want the people I care about to enjoy the things that I often can't enjoy. Go have brunch with some people you care about and really enjoy it, or go to the beach and have fun laying out in the sun, or read a book you really love. When I am suicidal, I can't do those things. I can't read your friends mind, but I would imagine that she would want you to honor her memory by enjoying life to the fullest as much as you can. Maybe that sounds cliche, but I really think it's true.