Some horses have to be taught to eat carrots, apples and treats.... Maybe try dicing the carrots into very small pieces, or you can do what I've done, lol, put them in your mouth, chew on them, then spit them back into your hand, she might try them like that or mabye put them in with her grain. Several of mine love mint candies and go nuts when they hear me unwrapping them. So keep trying,
If you want to put weight on her with food, You could try some stabilized rice bran, it has lots of fat. There are other foods, too, like shreaded beet pulp and bagged feeds from Purina, like Strategy... Thoroughbreds are well known for being hard to keep weight on and I've found that mine do best when given free choice alfalfa, which ends up being about 300 pounds of hay a week, but I've never had pasture, so I'm doubt that one on pasture could eat that much hay and grass, lol.
-Kathy
Edited to add: FWIW, if you got some alfalfa hay, you could also feed it to your peafowl... Miy peas eat just the leaf and lay their eggs in the stems, it is also a good source of calcium.