Do you do ground work with her from time to time to improve her sensitivity to the lead rope and her connection to you?
I know a lot of people do ground work without an emphasis on the hrose following the leadrope, but rather using their body language to "push " the hrose around. That has its place. But you want to work some on having her be so light to that leadrope, that just the weight of it is enought o show her which direction you are directing, including forward.
First of all, I find a rope halter very helpful for training, but not essential. And a good heavy leadline also a nice thing to have.
You want her to lead up promptly to your pull on the line. So, when you are in the leading position, just ahead of her head, have about 4 or 5 feet of slack in the leadline. YOu say ,"let's go!" and you lean your upper body forward, then you step off in a purposeful manner, you are going somewhere. If she doesn't move she will hit the end of that rope. YOu keep pressure on her (hold the rop firmly down against your hip, anchored there). If she still won't move forward or she drags back against the line, use the tail end of the leadline to swing around and "nip" her near her hip. She may react by shuhsin sideways or even backward. No matter, just try leading forward again. you got her to move her feet and that was your goal. So, don't change YOUR position if she backs up or goes to the side. If she does run out to the side, you start walking forward. If she actually runs past you, stop firmly and lift the rope and stop her, put her behind you again and start over.
So, you lead, she resists, you put the leadline or a whip on her hit (try to stay facing as much forward as possible when you do this) you break out her feet , then you both go forward.
Something tha is really important is that if she does move forward from your pulling or you suggestion with the whip/leadline, then dont' take up the slack she has created by moving forward. I mean don't like run forward. Just walk on. Her job is to keep slack in the line, your job is to not rob take it back if she puts it ther. The slack is taken up IF she refused to follow properly, but you dont' reel it in , or speed up when she moves up because that is YOU taking the slack out of the line.