First of all, you're a saint for helping her. My mother was actively involved in horse rescue and our first little mare took three years to be able to catch without literally wrestling her into a halter. She needed tranquilizer for everything. Teeth, feet etc. And every well known horse person in our area didn't have any better luck with her either. She flipped over when trying to trailer... that is if you could get her near one. She dragged you left right and center. Pretty strong for a 14hh Arabian. You'd see her going at full speed with a 200+ man on the end of her lead rope.
Shaddy needed time to settle down. She ended up turning into the most sane, dependable riding horse and now you'd let a little kid swing off her tail or nap under her feet.
Your mare sounds like my girl. Shaddy has taken down stall doors because she was afraid of being stalled!
An exercise I do with all horses that hate tying is teaching them first to stand still. If the horse doesn't know how to stand still untied it's not going to stand still when you tie it to something. It also helps establish personal space. Simply take a few steps away from her and keep her away from you. If she insists on coming close or moving from where you put her, put her back. Reward for any small, tiny improvement.
Good luck. Hope you can get a pro to come out and help you and your lady out. She'll be so much happier when she isn't on edge all the time. Shaddy is and is it ever rewarding to see peace in her eyes.