Start your ride on the right and reward any moment out, then ride on the left and reward any movement out (but this is the good side so basically just reward movement off of your leg)
Call chiro/massage and try to stretch her neck out by taking a carrot and putting it to her belly making her head turn to touch her belly ( this will help stretch out both sides and hopefully get her looser until a vet can come out)
I would make sure there are no health reasons for this. And if not then make circles pushing her off your leg. And also maybe try a spur on your right side
Also try to do leg yields and get her used to leg pressure so eventually if she does decide to drift from the rail you can always ask her to move back o
She's favoring sides and must be very off balance. Try shifting your weight and see what
thats if it doesnt have anything to do with her health. if so, take her to vet or chiropractor.
all horses have a favorite side. the best way i think to solve the problem is when you go in the arena START on the right. and maybe work her more on the right side then on the left. sooner or later she should start to do fine
I would start but getting her a chiropractor. I had a horse who bulges to the left after he fell down and was misaligned for a few months
I would suggest to not riding on the outside track for a long time and make small circles and other ground figures that you know.
I would also do more lateral work and leg yielding on the diagonal. When she wants to go to the outside track instead of really reacting to your leg, change the direction.
Go on the centerline and try leg yielding in Zig zag. Usually you can feel the difference of the leg reaction really easily with this task.
I guess when you do leg yielding to the right it will work easier then leg yielding to the left.
when her reaction Is better to your leg , try the lateral work in circles (15m ) small circles ( 8-10 m).
Make sure you use your right leg first to bend the ribs right at the girth before you use the right rein to bring your horses head in to bend the rest of the body.
make sure you keep her busy with different tasks for her to do while riding to confuse her.
After some time she will be so confused because she will never know where you want to go and what you want to do, she will give in.
You can always try putting poles parallel to the rail. Also more lateral work. She could just be really stiff on one side
I would take into consideration her health. Have a vet come out and check her for any lameness, arthritis, stiffness, etc. on her right side just to be sure, before forcing her to do something that may be causing her pain. :)
If so, use that as a third leg. Apply pressure with your leg on her ribs, and the crop on her hip. Also be sure that the bit isn't too harsh, and keep a slight bit of pressure on the rail side.
Do you ride with a crop or bat?