Clinton Anderson has a good method that I like. Get the long rope (60'?) and he uses his tie ring thingy. Run the rope thru the ring without tying or flipping the pin on his ring so the rope will slide freely. Once the rope is slid thru start despooking her and let her run backwards - as soon as she stops - stop doing what ever scary thing you are doing, relax all your muscles and expression and say good girl. Ask her to come back. Do it again, and again, and again. She will become more desensitized so that she has no reason to spook and not feel so trapped.
Here are a few Clinton clips
that may help. I do a lot of lunging for respect and despooking on mine. I couldn't find a tying video clip of his.
I have also taken a bicycle inner tube and tied the lead rope to that so there is more stretch before she can actually break it.
The one horse I had (this was pre-CA era) would break lead-rope latches for the fun of it. I got a hold of a Western Horseman scrapbook. There is a section in there where you make a gut rope. I took an old lunge line and looped it around his flank. Tied a knot in it so that when I clipped it to itself it wouldn't slide to loosely. I ran the end of it between his front legs and tied it just a little shorter than his lead rope. He sat back on it one time and never broke another latch after that. Now, keep in mind this horse did it cause he figured out he could - he was not spooking and would do it when the random thought crossed his mind.
And one last method. Hang a lead from a high point, like an overhanging sturdy tree limb, so that when a horse is clipped to it they can't get leverage to pull back. They can walk in circles, but not actually pull. It worked on my puller until he figured out how to twist the rope and unclip the latch. Gotta love appys! If I were a tree climber, I would have put one of those spinny gizmos on it so he could twirl the rope round and round and not twist it.
Hope this helps and at least one is something you can use.
My jittery colt that I adopted responded well to an hour in the round pen with my CA method. I was firm and assertive, but I backed off as soon as he gave to pressure. I got further with him in a hour, then the owners had in 6 months (which is how I came about getting him). I gave him boundaries, told what I expected, and backed off as soon as he gave it. Now I can do whatever I want with him even if he is wanting to shy. He will stand with my holding the halter and his side will quiver while he switches his mind over to me saying whatever it is isn't going to eat you, you are fine. Took a few months to get there and he has much fewer boogies that get to him, but when there is something nervy to him he knows I am alpha and I will take care of him.