Hello,
I was in a similar position not long ago, so hope this helps you a little. It's just my opinion and I am not a vet, just a rider. Your filly has a terrific little face and a wonderful expression. Her shoulder is nicely sloped and her neck angle looks good for dressage movements. In some pictures her back looks good, strong & short, but in others she looks built a little "downhill", which is great for flat speed, but not good for collection. It's really hard for downhill horses to get their back ends under them without straining their backs/stifles/hocks. My main concern, and it might just be the picture's angles, is her pasterns. They look very long and upright, especially in back. Her right hind also seems to angle out 15-20 degrees. This would be really tough for a dressage prospect to overcome as the concussive force of each step will be maximized. This will put undue strain on her hocks/stifles, which it sounds like you have experienced before. It'd also make for a very jarring ride. But it might just be the picture. I'd have a trusted friend/vet look at her for this though b/c it would definitely rule her out for dressage, jumping, comfy trail horse and suggest lameness issues down the road if they are long/upright. But every horse comes with something, right? If you are only doing lower level dressage & just enjoying her in other disciplines, then the attachment & personality counts for something, so it's all a balance. There's no "perfect" horse, but there is a perfect horse for every rider. Good luck...