I agree with Tinyliny; you've come along very well, Ellen!
Looking at your references, though, I noticed that the pony is a little bit off balance -- the front legs are longer than the back in your drawings. (Did you know that a horse's rear cannon bones are longer than their front cannon bones?
) A great way to help this problem is to draw a "box" or a couple of lines where the horse's feet are/will be (I suggest you use a ruler; most of the time, on even ground, the feet will be even). If you'd like me to draw something up real quick to show you I'd be more than happy to.
I also noticed that your pony drawing is more stout than your reference; this adds individuality to your drawings, but if someone is commissioning a portrait of their horse they want it to be as accurate to their animal as possible. Again, the square under the feet can help with that a great deal. Do you use a base? (In another way of asking: Do you use sticks, ovals, and circles before you start to draw the actual horse?) Using a base before you being the "actual" drawing purpose can help you spot out any anatomical errors. This is especially helpful for "young artists."
And OH my goodness, girlie, your shading is so spectacular! I love
it when artists shade their horse drawings realistically. It helps create a great sense of depth and can help set the mood of the image. Your shading just took my breath away. <3