Wow she's gorgeous. I am confused, though. If you know her parent, how is she a mustang? Isn't a mustang a feral horse?
FWIW I ride my Pony and I had a dressage instructor come out and give us a lesson. She said that he would be a great dressage horse, at least at lower levels. I asked her why, as he has somewhat choppy and small gaits. She said he seemed very submissive and relaxed while working, and as a judge (right, did I mention she also judges dressage shows?) that was really important to her. Basically she would have given him a lot of points just for his attitude.
Sorry, that doesn't really address your questions about conformation. I am not qualified to make any observations there, LOL.
"Saddle fit -- it's a no brainer!"" - random person