She sounds lovely :) Sometimes you do find these 'gem' thoroughbreds :)
If you are unable to get xrays, just get to know how she normally moves very well. When I started getting suspicious that there was something going on with my gelding, he'd been in 6 months of solid dressage work and was nearly ready to go out for his first official comp. He had always been extremely trainable and willing, not once did he put his ears back or get grumpy when I asked for something new. But he'd started getting a bit grunpy, swishing his tail, going to bite when I brushed him etc.
Everyone said the ottb was just coming out in him and to keep going, but I've worked with my fair share of ottbs and this wasn't the same. I was told it would be a waste of money going to the vet, but I could feel it in his movement that his right hind was just 'off', never lame, no one could see it on the ground, but it didn't feel right.
And sure enough, bone spur and arthritic changes in his hock. The vet was amazed that I'd picked it up as there was no clear lameness. And now, 18 months later he's still no good.
So just know your horse, take the work nice and steady, jump her if you want to, but just be very tuned into your horse and know if she's fine or a bit 'off'.