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!