I'm not sure if she is downhill or not. In the first one she doesn't look it, but the others, she does. I don't think you'd have any problems doing barrels with her, though. If you were jumping, the downhill thing would be a problem, but its not really a big deal if you're just doing barrels. :) She's cute.
These pictures arent great but she looks to be ok, the only thing that really stands out to me is her croup is kinda flatter than ideal. Her feet and legs look to be straight, head and neck ties in nicely and her back isnt long..is she in foal in the first picture? If not then she looks like she needs a diet and a workout