This is gonna be tough.
The number one thing that women go off of to guide them in the right direction are their feelings. In your case, if you were to tell her that you want to be with her, she would probably feel "weird", and it could cost you the friendship. But I also believe that anything is possible.
From being her friend for 2 years, she knew women you dated, you know her ex-boyfriend, she's pointed out single women to you, and even gave you advice on the women you dated which makes this situation close to MISSION IMPOSSIBLE. What you probably should realize is that when you're close friends with a female, she views you the same as she would a female friend. Basically, you're one of her "girlfriends", but you have a peni.s and no breasts. In her mind, this makes it highly unlikely that she would date you or find you sexually attractive. But this doesn't apply to EVERY female, just most.
In my opinion, in order to change all of this; her being your friend (of 2 years) to being something more... the work you put in may take just as long as it has being her friend. You have to switch the momentum somehow, get out of the friendzone (which is probably equal to giving people in hell ice-water), and from there, initiate attraction (which you can read about in many directories in the forums), and try your luck. But it may cost you the friendship in the end. My best advice would be.. find other chics, because I also get the feeling that if you were to get this chic, you would only have interest in her, and no one else, and it wouldn't last long.
