"I don't understand why this is so hard for me..."
Because you backed yourself into a corner and you won't own up to it. You drew a line in the sand where you shouldn't have.
"W, you are right. It is not respectful or decent to keep her as a FB contact if in my own mind I am still interested in possible reconciliation. I am. I deleted her. She is not a friend to our M, so she does not belong in our life. Sorry it took so long, I painted myself into a corner with my big stubbornish brush."
