This sounds like a perfect candidate for one of Ramon's (my Spanish Instructor) games. Basically she needs to understand long and low (true long and low where the horse is both engaged and pushing the bit forward).
I'll try to explain the game as best I can, please take all descriptions at their most generous.
This game may take minutes or months (many sessions obviously
). The goal of the game is to have a horse which looks to work long and low as a response to contact. It is played at the trot (later you can also play at the canter but it is slightly different) - you sit back and simply ride, the horse does all the work. Sit back and to the inside - take up a short (not nasty, not EVER pulling back) contact on the inside rein and a light contact on the outside, so that you horse is strongly flexed to the inside and ask your horse to trot on a small circle. The game is that if the horse raises it's head, hides from the contact or has a hard contact then you bring your inside hand to your hip and the horse must circle very tightly. You do not allow the horse to slow to a walk - it must trot forward. If the horse begins to soften its mouth, relax its neck, put its head down and forward (any or all) then you release your outside rein a little more so that the horse may stretch its neck a little more. If the head comes up, contact hardens etc etc then the circle tightens (you must sit back! and inside).
Even if the horse doesn't 'get it' at first - change the direction every few minutes (obviously changing the contact etc) so that the neck isn't hurt or the horse (or you) get too dizzy. The key to this game is that you must keep the horse working and not work yourself - i.e you can just sit there - don't get annoyed or anything - just hold the rein and immediately give when the horse gives. You must be very responsive and allow the horse back onto a larger circle whenever it starts to try going long and low (pushing the bit) and also bring it back onto a small working circle if it decides to rush, stick its head in the air etc. As the horse begins to understand you ask for a little more until the head is down near the ground and still pushing the bit (while the horse works properly from behind)
I hope the description doesn't sound crude - it is both a very simple and sympathetic game and quite complex because you must know when to give and how. The horse gets to work things out on its own and because you aren't constantly nagging at it or fiddling with its mouth it doesn't see your hands as the 'enemy' if you get what I mean. In fact, you really do very little and this seems to both calm and confuse the horse a little. They seem to 'understand' that the rider is not 'doing' anything and it is therefore fighting with itself - instead of fighting it then simply tries different things to work out how to get out of this uncomfortable position - you reward the desired behaviour - going forward and down. This is great for the horse because the desired behaviour is also the comfortable behaviour - win\win!
