I worked with her on the ground yesterday and she listens very well on the ground! She whoas whenever I stop and I think she is learning my voice commands. The dentist is coming out in a couple of days and I REALLY hope that is the reason why she doesn't slow down easily. So everyday that I can't ride, I'll just work on ground manners with her. She did sooo amazing yesterday!!
But whenever I was riding her and I took her from a trot to a halt, she started to back up right away. And then I squeezed her so she would stop backing up and then she jumped forward and got really antsy. How do I let her know to stop backing up without making her jumpy?
I really think you are not understanding what we are trying to tell you.
You've created bad habits in your horse that are probably going to take WEEKS to fix, if not MONTHS.
Can you imagine this for me for a moment? You are holding the bit in your hand, and I am holding the reins and bridle attached to it. I tell you to start walking in front of me. I tell you when I want you to stop, I am going to pull on the reins. But instead, I pull the bit HARD, so that you almost fall over backward. I tell you to walk ahead of me again. What do you think you'd do this time? You are going to BRACE for my hard pull, and you are going to PULL BACK on me in order to keep your own balance. You've just created a situation where I need to pull, pull, pull to get you to stop. But you are going to brace against me to keep yourself from falling over backwards. Hence the vicious cycle.
Does that make sense? This is how your horse is reacting. Yes, she may have a dental issue, but 90% of the time, it is the rider's fault
for the horse's behavior. You have been over-pulling on her mouth, causing her to brace against you, or even ignore you, becuase you probably don't stop pulling when you should.
Taz Devil and FaceTheMusic gave you great advice.
You do not need a change of bit (minus that fact that a Tom Thumb is a piece of garbage and should never be put into a horse's mouth), but you need a change in the way you ride.
How are you going to get your horse to slow down in a western pleasure class? You certainly won't score well if the judge sees you pulling and pulling on your horse's mouth.
We can incorporate this training into your ground work. Start with a bit that does not have shanks (a snaffle bit). Stand at your horses left side. We are going to ask her to bend her nose to the left. Using the "inside" left rein as a direct rein, put a small amount of pressure on the rein. Wait for your horse to respond correctly. Since she already has bad habits, she may pull against you. Or she may try to walk away. You hold your position steady. Do NOT pull harder. But do not release her. If she walks, you move exactly with her to maintain your position. The very instant
that she creates slack in that rein, you need to release the rein pressure NOW. Immediately. Pet and praise. I don't care if she only moved her head 2 inches. If she created slack in the rein to find her "release" then you need to release her. Repeat on both sides until she moves her head a small amount either way.
Slowly and gradually ask her to move a little farther in her bending. Eventually, she should bring her nose all the way to the saddle.
Incorporate this same idea into backing up and/or stopping. The very instant she responds correctly, release those reins. She needs to get a reward for doing something correctly. That reward is pressure release (that you have not been doing correctly up until now).
I strongly recommend you work with a trainer to show you how to do this in person. It's very hard to read something from the internet and put it into real life.
Either way, you need to re-train your horse to listen to the bit.