Sorry for the short comments earlier. I responding from my cell phone and its a pain in the butt to type long comments.
This is what I see:
This mare needs weight. Getting grained twice a day means nothing. She isn't emaciated by any means, but I think that she would benefit from 100 lbs or so. Also, she needs muscling. Big time. She has very little muscle anywhere. She would greatly benefit from hilly trail rides, and trotting in sand. She is also strung out. Her hind is not engaged at all. This can be improved with more transitions. Because she is strung out, the is also heavy on her forehand. Right now, all of her weight is on her front. When you shift her weight to her hind, she will become engaged and her front end will move more freely.
I maintain my thoughts that she is not ready to be jumping. If you were a little thin, and had no muscle, you would not enjoy jumping hurdles. It takes lots of time and effort to get a horse into jumping condition. I would work on lots of dressage for now. :)