Skyeternalangel is talking about the first video I recommended for you...I think anyway. :0) That one is the first of a 3 part series on de-spooking your horse but part one gives you a quick lesson on getting started. Here is the link again: http://.despookingyourhorse.com
Her reaction is quite normal since she doesn't know any different. She knows food means "go eat food". So she reaches out and persists. This is the behavior that has worked for her so it is the behavior she will repeat until we teach her a new behavior. This is part of how they learn...learning what works for them to get what they want. Also you pushing her head away can turn into a game that she enjoys so let her make the decision on her own. When the horse is allowed to make the decision it always results in a much stronger behavior. The lesson is much more solid. This is why liberty work is so important when teaching the basics...but I am getting a little ahead of myself.
Start by having the food in something small enough that you can control access and easy enough for you to get in and out of quickly (and waist pack usually works pretty well). I recommend standing by her shoulder facing forward and I would recommend sliding the waist pack around to the side closest to her. This way as she cranes around to reach for the food, the stretch is hard and at some point she will put her head forward to get a break from cranking her head around. I recommend starting with the smallest LOOK away from the food. The instant you see her eyes look away click and feed her a big handful. Reach you hand out and feed her where you would like her head to be (out in front and slightly off to the other side). THis practice will help to take the focus off of the food source. While she is still chewing, and not yet focused on trying to do something to get more food, click and feed her again (as long as her head is still away from you.) This will be setting her up for success since she is most likely going to be doing the correct thing...something worth reinforcing. Pretty soon you will add more time in between but to start you need to build a good reinforcement history with the correct behavior and this helps to make the criteria clear for her. Continue this for about 3-5 minutes each session. You should see her start to put together the new behavior that results in the food she was trying to get in the first place. She will realize that turning my head away/standing quietly results in food but pushiness gets me nothing. You have just replaced the old behavior with a better behavior. This new behavior requires that she wait and watch for you. Repeat this lesson twice a day for about 4 days.
This training period does two things...1) It teaches her this new lesson, which is manners, and reinforces it quite a bit so this becomes her default behavior. and 2) which is even more important is: it gives the clicker, or whatever signal you would like to use, value as you pair it with the food. This is called classic conditioning and it is the same principle behind Pavlov and his dogs. Pretty soon the clicker communicates you just did something correct and you have earned yourself some sort of reward. It actually bridges the time between the time when they perform the correct response and the moment when we can reinforce the correct response (bridge signal). When she is getting this sorted out and is doing well you may try walking a bit and maintain the same criteria. This really cements her respect of space. After the 4 days I recommend going to the target training (also on the first video). This portion of the training teaches her to step up the game and begins to move into the working relationship. It is easy and the horses love it (you will too). I recommend repeating this for about the same amount of time as with the the clicker...4 days, twice a day for about 5 minutes.
After this, you have laid a solid foundation and you are ready to go where to any behavior you would like to work on with her. The target will be a very useful tool for all sorts of behaviors. Think of it as your new halter and lead rope. You can use it where ever you would use the halter and lead (leading, trailer loading, lowering head for clipping, ground work, leg yields from the ground, introducing new objects, focus, holding still for mounting, backing up...the list goes on and on!!) Through all of these lessons try to also draw attention to relaxation...a softening of the eye, ears, mouth, lowering of the head, exhales and relaxing of the muscles in general. This will get her to learn to relax and focus. Still start by looking at the correct responses (turning the head away and later, touching the target but keep an eye out for relaxation as well and draw more attention to these things as well. There is also a blog post about relaxation and attitude and it should be an underlying theme for all training. Here are a couple other tips that may help: 1) I recommend feeding generously when getting started. This helps to make a big impact and lets the horse relax because the food is coming. Sometimes little tiny handfuls may almost seem like a tease. 2) remember to only click and feed the behavior that you would like to see more of since what gets them the click is the behavior that they will repeat.
Okay, so there is more of an outline but as I suggested I recommend sorting through the blog links that I gave you earlier. There is a virtual treasure trove of information there (video and written). Here is that link for the blog. Remember that you may use the search bar to look for specifics. On Target Training with Shawna Karrasch
I look forward to hearing of your progress. :0)