pulling into the middle

I'm helping the barn owner train a 4 year old mare to hopefully get her a little farther before she's sold...she's great when she goes clockwise...but she always turns in to the middle when you trot counter-clockwise.

I'll get her going and when she turns in I'll put more pressure on the inside leg/hip, open the outside rein, and so on...but she doesn't respond to it. We worked on that for a good 30 minutes and with no improvement at all.

What else can we do? Any ideas?

Hello! I would try to keep it as simple as possible, as the horse is only 4...so what I would try is as you are riding around on no specific track(that way you don't get 'stuck' on a circle or whatever pattern), pay attention to which directions she chooses to take. So if you're walking around and she feels like she'd like to venture left, kindly turn her in a circle to the right, and then release once straight again. Leave her alone until she chooses to take a direction, and turn her the other way. So basically you keep contradicting her choices while keeping it pure and simple for her to understand. You can do this at the trot as well, and the second she takes you in a direction without being asked to do so, turn her the opposite direction and continue on. By doing this over and over she'll begin to understand that when the peace and reward is given is when she is traveling straight. And she'll learn to wait for your instructions rather than taking it into her own hands.
Good luck! :) Hope that helps.

When she does that turn in into the rail and do circles. The more she does it the more circles you do.

she knows the cues we all use to get her over to the side while both trotting or walking. Also if I have her do a circle...she stops trotting and will walk. Or she'll toss her head all around and threaten to buck or rear on me. Even if she did I'd ride through it...but we don't want her to start bucking because she doesn't want to go the way we want her to go.
I will try doing the opposite of what she wants...maybe it will work

If she gets 'stuck' doing the circles, make bigger circles so that it's not too hard. Practice hurrying her feet around on the circle so that she doesnt slow down while making the turns. If you're walking, hurry her into a crisp walk, if you're trotting, hurry her trot around the circle. That's also a good submission exercise and it will get her more focused on the job.
If the cue to push her over isnt working, move on to something else.
If she pitches a fit when you ask her to turn, it's a great opportunity to build a fire and then put it out. The more 'fires' you put out in a horse, the better they get. If you avoid the fires she wont get truly better.
If she threatens to rear, make her move her hind quarters over. A horse cannot rear if their weight is on their front end.