Coping With My Friend's Suicide

My friend, Tara Swain, was a senior at my high school, Independece High School. Last saturday (05/05/07) was our Prom, and no one saw her there. A few hours later, comes the report that she has committed suicide by sitting in her car with the garage closed, taking her sleeping pills (she was an insomniac), and eventually suffocating in the carbon monoxide.
I got very angry at first and asked myself what would have made her done such thing, and then the tears came. I couldn't concentrate at school, so after a few hours of being in the library with a group of my friends who were friends with Tara, I left and went home.
Her suicide had a big impact in me, especially because I've considered and attempted suicide before last year, and she had always helped me thorugh those difficult days. I feel bad for not being there for her.
I wish I could've done something to herlp her. I was always too busy to hang out with her, and I never saw her suicide coming. It completely took me by surprise, and I was in utter shock when I found out.
I just feel so useless. She killed herself and there's nothing I could do. I've contemplated on everything I could've done to save her, but nothing would have worked at all. Now I can't smile. I can't eat. I feel like I'm a rotting corpse. I don't know how to cope. I think I need help.
I wish she was here.
I miss her.

Goodbye, Tara.
I love you.