I don't know what she looks like, so I cant tell you how she looks.
There are a lot of people on the HF that know a LOT about horse nutrition, so if you want to learn a thing or two, you are in the right place!
Personally, I would take her off the corn. I lost a horse to colic (and the vet and I are both relatively positive that corn caused it.)
You can give her oat bran oil, flax seed oil, and beet pulp. They are all very good for putting on weight and great for the coat.
"The barn taught me passion... Not the passion of winning-but rather the passion that you feel when you have nothing left but your love of something. The passion that is there when exhaustion steals your strength and frustration takes your hope."