I would shy away from the butt rope. You really should take this slow without force or any more pieces of equipment to get her frightened of.
I like the idea of just going out and playing with her, just putting the halter on and doing nothing with it.
I also don't like this pulling thing, it creates bad leaders in the long run. You need to teach her first to move sideways from pressure, and then in circles and gradually to lead beside you. Once she has figured out that the halter is not a trap that stops her from going forward, she will be much easier to lead.