Can you try getting harrisons high potency mash and sprinking it over her seed? Harrisons also makes something called recovery formula for anorexic birds, ailing birds. Here is a link to the recovery but the high potency mash can also be seen on their website.
If it were me, I'd also get a good quality vitamin to add to the water due to the circumstances of her not eating well. At least it would be one way to get some vitamins in her system. Avitec has good products that dissolve well in water. Check this one out and see if it would work http://www.avitec.com/AviVita-Plus-M...ement-p/ap.htm
Some birds also really like peanut butter toast or toast with baby food smeared on it, like squash or carrot baby food high in vitamin a.
Another suggestion is high fat things like nuts/seeds (almonds, peanuts, pecans, sun flower seeds). A lot of parrots love those.
Bird bread is another option that you can add veggies and pellets to. There are a lot of recipes online. Some people use the jiffy corn bread mix as a base because birds tend to love the taste of corn and then add things to it. You can start with seeds to peak her interest in it and then sneak in a little veggies, pellets, fruits, etc.
Once our pets get older and thin, I just give them whatever they'll eat. I am going through this with my 14 year old cat who was slightly overweight two years ago and now is pretty thin. She won't eat any high quality foods. Only the cheap foods and treats. I'm like okay, as long as she eats!