You HAVE to let her think that YOU have ALREADY moved on.
THAT is the key. She needs to feel that SHE screwed up and that you are not interested in her anymore. You will be wasting your time with any other plan. You need to get her to the point where she asks YOU what is up with you.
You then say to her... "Well, I have done some thinking and I decided that I want to be with someone that WANTS to be with me and shows me that they want to. You seem a little wishy washy and I realized that maybe we are not right for each other. I think we should JUST be friends. I am not ready for a serious relationship."
And then get off the phone and leave her alone......
She need to realize that she may have gone too far and not treated you right and YOU need to man up and call her on it by showing her you have moved on. You need to quit talking abouit "closure" (that is a feminine term) and start TAKING the closure in your own hands. Men who are successful with women don't keep hanging around like you are.
Let her feel dumped and allow her to chase you. She is never going to be attracted to you unless she sees you are some tough cookie who demands better from his women.