Owner of a sometimes herd bound half-percheron here!
I find it really helps to start work IN the pasture. If I grab her, bring her in and THEN try to work her it just flat out doesn't work. I have to start working with her the moment her halter is on.
Halter her and just walk around the pasture. Be meticulous with discipline - she must stop exactly when you do, walk exactly where you want her to, or she gets backed aggressively. When exiting the pasture, she comes out the gate on YOUR terms. The walking perfectly helps me a lot - we walk at MY pace, and if she doesn't follow me absolutely perfectly she gets a good bit of backing or circling.
Alternatively you could try what I do sometimes - I'll make her work HARD right outside the pasture gate. Then we walk away and stand, with her facing away. The MOMENT she turns to go back, we go back to the pasture gate and work HARD. Rinse and repeat. She figures out pretty fast she doesn't want to be by the gate, because it's hard. She can rest if she stands quietly where I want her to.
Ultimately it's a matter of not letting her get away with ANYTHING or she will take advantage of it. I can just haul her into the arena and work her, I have to address every misstep on the way there. It keeps her focus on me and earns her respect - she HAS to be focused entirely on me because if she does wrong there's repercussions. It helps a lot to be meticulous with manners. No, you can't have your head near me. You can't start walking before I say. You can't walk ahead of me. You have to match my pace. Etc etc.
It could take a few days to make it to the barn. Start very small. Work her where she's comfortable so she learns what you expect (in the pasture) and then start to bring her out, keeping those rules you introduced solid.
Give it a go. It gets easier as you earn their respect and trust. She doesn't know that she can trust you, and she has no reason to respect you yet. It's up to you to give her a reason. It won't always be this way - hard rules, etc - but until she's not a danger any more she gets the hard end of the stick. It IS fixable, it's not a reason to give up. It just takes time and determination.
ETA: It all comes down to who controls the feet. If you control her feet at your whim, she's much more apt to have respect for you.
Last edited by Shoebox; 04-23-2014 at 02:11 PM.