Keep doing what you are doing, but if she doesn't want to back, make him move her feet by doing circles. Then go back to backing. If she takes ONE step back praise her and do something completely different. Come back to it in a little while, and repeat this process, but ask for more steps backward each time.
I want to say that I know everyone has their own way of doing things. With that, why do some make it so complicated?
I am like montcowboy. Keep things simple. First thing is you need to have patience. If the horse is not focused on you, do something to get it, like flexing or even doing circles. When they are focused but refuse to move, I would just hold a little more pressure on the reins than just making contact with the bit. Just keep that pressure steady as they do what they will do until there is one step back. Only then would I release. Any sooner, you just rewarded whatever they last did. It might take 5minutes or half an hour. Out wait the horse. Let the horse think about it for a few seconds and ask again.
I would not be flapping my legs on a horse when they are learning to back. That can easily send confusing cues to the horse. One you are telling it to move and more likely it understands as move forward. The second you are blocking or stopping forward movement. Instead of the horse being able to go forward, it goes up as in rearing. That is exactly how you teach them to rear. Posted via Mobile Device