Thanks everyone. I have to wait until the next shoot to see what happens.
I can use a flash, in fact, I can set up two flash units with my triggers if need be. I might do that and bounce them off the walls. I'd figure they would give good coverage at least to a certain distance. To be honest, I never thought of bouncing the walls. That's why I asked here, because I knew sooner or later somebody would come up with ideas that I was either forgetting about or didn't know about. If I had my head out of my butt when I was shooting I would have tried the walls, but the thought never crossed my mind. I got to the point where I was defeating myself before even pressing the shutter. I don't think the horses pay much attention to the flash, I've used direct flash right at them and they don't seem to flinch. I always ask beforehand if i can use a flash, just in case the trainers decide not to let me.
I am going to shoot higher ISO and RAW, and will probably bring some gels with to test. I think I have to give up on distance shots though, which is gonna suck because a lot of the time she's in the back where I can't get to. I might ask them if I can get inside the arena and shoot from the middle somewhere, maybe the light is better inside instead of shooting from the side.
now i would like see new shoot.
About a week and a half, next lesson is on the 4th.