This is a question that comes across my desk on a regular basis, and I have yet to find a universal response. You see, every situation is different, and every person will and does react in ways that I cannot predict. There are no quick fixes, and each option I present will take time. You cannot force yourself into or out of love with someone. The human heart doesn't work that way. What you can do is begin to move on.
Normally, the first step to that process is admitting the truth. Tell the person in question how you feel about her, then explain to her that you are not going to pressure her into anything she does not want. You are telling her in order to set yourself free while maintaining the friendship you hold dear. If you do not feel telling her is an option, then, depending on the depth of your emotions and the length of time which you have felt them, essentially cutting yourself off from her is the next choice. In a way, you will go cold turkey from your friend. I am not suggesting that you simply cast off your friendship to save your heart from more pain. I am suggesting that you give yourself time away from her to start moving on. Don't run to her every beck and call. If she desperately needs your friendship, that is one thing, but you cannot allow yourself to be left on the back burner. You have to put yourself first.
For many, this is not an easy concept. So many people who write to me are the kind who are used to putting the needs of others ahead of their own. You cannot do this if you want to move on. You must think of what's best for you first and foremost. It is not selfish; it does not mean that you will stop being a friend. You must think about how every action and interaction will affect you if you truly wish to preserve your friend and open yourself to new love.
I do wish I had a quick fix for this, Mister E. Our lives would be much simpler if we were able to turn love on and off like electric lights. The universe just doesn't work like that. I know these options are frightening, but you showed strength in writing to me, so I believe you have the strength to do what is best for your heart. If you need an impartial sounding board, you know where to find me, and I will do my utmost to help you in any way I can.