Everyone here has good ideas! The most effective one for such a horse IS to start at feeding time....The method I used was putting the hay/grain where they can see it, BUT, make them respect your space by 'pushing' them away from it untill YOU say it's ok to eat. This is a GREAT exersize that I use EVERY time I feed, even with my 4 year old mare I've had since she was 2...I HAVE to make sure my horses respect me on the ground because I deal with drafts and draft crosses. The other thing is, is that you CAN give treats...just not by hand....Carry a small bit with you (prefferably in a plastic baggy so it's harder to smell) and when she has performed a task well behaved (such as leading from point A to point B without rearing, kicking, or nipping) Take a treat, put it on the ground, then again impliment the "You can have it when I say so"
I understand having limited time to spend with her, but at that age, 1 hour is a LONG time! Now if you CAN make it out there more often, perhaps not for an hour at a time, that could help alot. Keep consistant too! And DEFFINETLY get foal feed. There is too much sugers, startches, and carbs in adult 'grain'. I would also sugest a pelleted feed as that is good for digestion as well and will lead to fewer "uncomfortable" tummies, which will lead to a calmer all around horse.
Make as much time with her as possible into a 'lesson'....Even if it's just you petting, scratching, grooming, or leading, keep a crop or small whip, or a rope if you preffer, with you to use that as a simple extension of your arm. Also, do NOT let her 'lip' you. If she lips you, it 'could' lead to a nip. Now, you don't have to pop her one for lipping, just move away from her lips. You have to be in control all the time, especially with such a young horse.
I know this seems like alot, but really, both you and your new luv needs this.
Another thing that you can do to help your 'bond' is that every few minutes that you spend with her in your aloted hour, just get up close to her and TALK to her...doesn't matter what you say. Sing 'Row Your Boat' or even 'Girls Girls Girls'! This lets her know that you're 'ok'...this gets her used to your voice and I KNOW it sounds sooooo weird, but it works! When I got my mare, she was jumpy, 'lightly' abused (previous owners just didn't know how to handle her) and just a little 'crazy'....When I'd go out there I'd just talk to her and be myself and before I knew it, she was walking up to me to say hello and be affectionate...it took a few months, but in the long run, months are mere minutes!
I hope this helps and I wish you the best of luck!