(((((Here's a big hug to start things off.)))))) All that you said makes sense. Suicide has touched my life as well, a good friend a while ago who had a lot in common with your dear friend, and my brother-in-law last summer. I can relate to having to remove yourself for your own sense of self-preservation. Do not blame yourself. There are just some things in life that we don't have the power to control.
With my brother-in-law, Owen, his wife had left him and taken the kid the furniture and any hope he had left. We all knew the circumstances. We knew he was depressed. My husband and I made plans to have him over for dinner that night. He said maybe, that he wanted to see if he could get to see his daughter. That was the most important thing to him--his kids. He had another son to a girl that he had bought a ring for, but she decided to back out and take the kid with her. (More heartache on top of heartache. Now he has lost his second child.)
I beat myself up because I didn't go running down to Owen's house and guard him, protect him, keep him from doing something stupid. But you can't make being their protector your entire life. It's too much responsibility for any person -- even for a parent. Even if I could have prevented Owen's suicide in that moment, that night, what about the next, and the next after that? I have come to realize that I couldn't stop that decision. It was bound to happen sometime. Just as you explain in your posting -- your friend's suicide was imminent. I believe I heard the words, "Suicide is the end to one person's suffering and the start of everyone else's." That pretty much encapsulates it for me. We may be relieved that our loved one has been taken out of his/her pain, but that leaves us to sort everything else out. Free yourself from the guilt.
As far as saying "goodbye" -- are you a person of faith? You don't necessarily have to be a "go to church every Sunday or temple every Saturday type." I consider myself an amalgam of Christian and Buddhist. I listen to nature. I'm spiritual in the Native American style. But whatever your style, God, Mohammad, Allah, Jesus or the universe listens. Say goodbye to your dear, sweet friend now. Talk to her. She can hear you. And if you listen very carefully, she'll speak back to you--sometimes in subtle ways, and sometimes clear as a bell. Light a candle in her honor. Have a birthday party on her special day. Celebrate the special person she was in whatever way makes you feel better. She'll know, and love you for it.
From the date you posted, I imagine you may have worked through some of these issues already. I'm just a newbie to the site and so I wanted to add my thoughts to your journey of healing. I'll be thinking about you.
Love, peace and strength,