You're right, she doesn't know what she's doing. All she knows is what she's feeling. That's what drives most WASs. I agree that it often seems like they're insane; throwing away a long relationship, trashing finances, and hurting children. But all they can see is some NeverNeverLand that will fix the hole in their heart.
I hate feeling the way I do, this ever-present weight upon my chest, this sense that my heart is just beating millimeters from the skin of my chest. The mood swings, the anger, the grief, the sadness, the guilt. It all just sucks.
Letting go, really letting go will take time and strength. Time for your heart to mend, strength to accept the reality that she's leaving. If you really want to get over her, think of all the bad times. It's natural to remember all the good times you've had, but do a 180 and think of every time she put you down, or denied sex, or any of a million things she did that drove you crazy. No relationship is all wine and roses.
My brother in law lost his daughter to murder in 2005, the same year I found out I had cancer. He still hasn't recovered, and has lost much of his sense of humor. I don't want the death of my marriage to do the same to me. I want to live and love with an open heart; and to have someone love me, warts and all. I've accepted that my wife doesn't. She may later at some time, but I can't wait. We're only given so many ticks on the clock, and waiting for someone to come out of their fog is costing me my life.