Is she chubby? Shedding some of the excess weight will help her supple up immensely.
Otherwise, you're basically on the right track, you've just gotta work slowly and build up the amount of 'tight' work slowly. Work on laterally bending her neck, so you can loosen those muscles. You can do that on the ground and in the saddle. Using your lead rope just take the slack out and rest it on her wither, and leave it there till she gives; as she gets better she will bend right round to her shoulder, without you even pulling that far. Then she should be suppling up enough to start doing more undersaddle. For lateral work undersaddle, you'll bring one rein to your hip, give her pressure with that side's leg, and leave it there until she stops and gives. Do with both sides.
You can also work at disengaging her hindquarters; again, an exercise you can do on the ground or undersaddle...I like to start on the ground (especially if a horse is un used to work), that way you aren't interfering much. Stand at his shoulder, and point at his hip with a dressage whip, if the horse doesn't move away with the intent, then start lightly tapping until he does; what you are looking for is for the near hind leg to cross in front of the off hind leg...When that happens stop, and praise the horse! You can do this several times in each direction. When you do this undersaddle, you'll bring the rein back like you did with lateral work, only you're going to bring your leg back further; for the first few times, or weeks, you may have to exaggerate the position, and almost bring it back to the rear cinch, but put pressure there, and hold the rein pressure, until you feel the disengagement of the rear.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."
Last edited by mom2pride; 07-21-2009 at 12:48 AM.