I completely agree with AQHA13. And whatever you do, I can't say this enough, DO NOT have any fear or uncertainty when you approach, lead, or ride a horse. I know it is incredibly hard sometimes & human nature, especially when you've had bad experiences but when you do have these things built up inside you, you will only get more bad experiences and bad results. Your horse needs to see you as a confident leader and someone she can feel completely safe and protected around. Groundwork exercises are an awesome way to earn your horse's trust and gain confidence with a new horse, or any horse really.
I just bought a new gelding about 2 weeks ago and just moved him to a new facility yesterday. He can be pretty spooky sometimes, especially in unfamiliar surroundings, but he's so much better when he is handled with confidence. He really responds to a relaxed person. I will be doing some groundwork exercises with him tomorrow. Let me know if you want to know how it goes so you can try them with your horse, I'd be happy to give you advice as you progress with her.
A good tip for being around any horse: Before you even go to the barn, set your goals. What are you going to get done that day? After you set your goals, physically & mentally let go of all the stress you have inside. Take a big, deep breath and relax. Release any tension in your body & be loose. When you go to your horse, handle and/or ride her, keep reviewing your goals in your head as you go and 'know' that you will get them done. When your horse senses that you have everything under control, it feels it can relax and trust you. I don't know how they know what we are thinking but they do!
Now if worst comes to worst and your horse just doesn't want to listen, DO NOT get flustered or give up! Just brush it off and try again until you get your goals done. If your horse refuses to listen still, keep yourself calm, don't freak out. Just move on to something else. This way you're not 'giving up' on your goals, you're just setting them aside and doing it in a little different order. Just remember to breathe and stay relaxed! I really hope this helps you and anyone else who has these type of problems.