have you tried just sitting on the ground and letting the horse approach you? If the horse is frightened, you sitting on the ground and not paying any attention to her (bring a book, draw, listen to music, text a friend, etc) will put you in a non-threatening position, and with you flipping pages, or moving the pencil, it will sooner or later spark her curiousity.
Also when I got my mare, I couldn't walk directly to her. When a large cat goes to attach their prey, how do they approach? In a straight line! Try going at an angle, keeping your eyes somewhat low and your belly button away (not facing her). If she show's fear, take 3 steps back and wait. Approach and retreat will do wonders.
I myself am not a fan of join-up as it's taking an already confused horse, and asking the horse to move all around you and to keep moving until he/she comes to you. IMO it works good for a hard to catch horse, but not a horse that is scared out of his wits and isn't comfortable with people