Hmm... have to disagree with clementine... She is a very mice build, well proportioned. She looks like she has a good neck I would just build more of a top-line by doing carrot stretches and back curls.
since you are just lightly riding her use this to build muscles and she will fill in more when she gets older. She looks powerful and well muscled behind! Good find on your part!
She is upright and short in the paster so I could be careful for things like ring bone, osselets, and splints. And she is a bit knock kneed so splints would be something to watch out for.
She is very filled out and not gangly for a 2 year old which is great! She is very pretty and