How old is she? She is camped under in the hind legs (sickle hocked is the other word for that) and her back is quite flat. It almost has the mildest of hunter bumps in front of the pelvis. That and the way she stands camped under make her look like her back is out or something. But it's not, right?
Her hind hooves are very upright, and that's what looked kind of club footed, but the soft earth makes it hard to see clearly.
Her front legs are nice and straight and she seems to have good bone, all around.
Her neck is set on a bit low, and very much undermuscled, but that might be her youth. Head is kind of big in relation to the body.
I cannot say how she is for barrels. My knowledge of what makes a good barrel horse is just not there.