So, I'm not an expert, but I really like the last one the best. She seems to have decent conformation from what I can see. solid legs, cute face, and nice angle to her hip and shoulder.
The first one seems to have a longish, sort of flat back, and it might be the way she is standing, but she looks a little cow-hocked.
The second one is long-backed and her hip seems too small for her well-built front end. Her hind legs are weak compared to her front. She has a cute face, but her eyes seem a little small. (I like big eyes) :)
The third one is really hard to judge because there aren't any close up or conformation shots. I do like her color though!
Hope that was semi-helpful! :)