Please bare with me as I am just getting the hang of doing a full horse confirmation critique.
Ok so her head and neck - as far as muscle she lacks a lot of top line, what is her workload. You say dressage but do you work her in an outline, long and low?
Her neck does look quite small on her body but I think muscled up it would look a lot better.
Her soulder does look to be a bit straight in my opinion but i've seen straighter! She isn't over at the knee and is nice and straight. The ground does look un-even so it's hard to say whether the bum high is her or the ground.
The front left is definitely turning out whilst the other turning in. I would agree she looks slightly cow hocked but yeah try getting another pic and see if it's the same. Looks a little bit sickle ocked but the angle of the pic isn't great.
I think she is nice though and I am being quite nit-picky, as far as certain areas of muscling then it's pretty much everywhere. But especially her topline. Maybe some hill work would be a good idea plus carrot stretches that sort of thing. She'd look much different then