About five years ago I was badly wounded by someone who I thought was a friend (in a church). I just recently ran across the person again on a social network when she put in a friend request.
I have to say, as much as I have tried to forgive there is still a certain amount of pain and anger associated with just hearing her name, let alone her wanting to be a "friend". Trying to stay on higher ground, I allowed the friend and that opened up numerous "real" friends that I had lost touch with after I moved out of state.
I agree with you, unfortunately. I don't know that the sting will ever go away - it just doesn't hurt quite as badly anymore.