I am going to go against the majority and say that she is palomino. Some people might recall me referring to the colour that 'gleams' on the coat. In this shot, you can see a fairly good example of the goldeness of the light. If she was a chestnut, the gleam on her coat would be bronze or copper, but this is a definite golden hue.
I would say that she is palomino with sooty. As a previous poster pointed out, sooty can cause the mane and tail to darken, as well as the coat.