My boy is clipped, and never flew even when he wasn't. But he likes to "fly" on my finger. If you put her on your finger and start running, she will flapher wings. I do this with Matisse nearly every time I go to pick him up. Now as soon as I pick him up he immediately starts flapping his wings in anticipation. I pick him up a lot, so sometimes we end up doing this up to 10 times in a day.
I also make him do pull-ups. I have a huge rope twist that circles the entire width of the outside front of his cage and whenever I put him back, I put the rope level with his beak, forcing him to pull himself up. He also likes to run the length of the rope.
After reading up on atherosclerosis in large birds I have been trying to find ways to make Matisse do more physical things. It is hard, especially for Eclectus who aren't usually known for their high energy. Here is a nice article with a section about cardiovascular health in parrots
https://theparrotuniversity.com/my-bird-gets-enough-exercise-doesnt-he
I find it interesting that it mentions raising HDL cholesterol. I am going to look into getting a metabolic blood panel done on Matisse to see what can be improved diet wise. He also has gotten the dreaded overweight status from the vet the last several times.
Also make sure she get some sun to help process vitamin D. I imagine indoor birds could become lethargic due to low vitamin D. This means if she is not in a spot where she has access to sun, bring her around to a sunny window for several minutes a day, or sit in the car in your driveway with her, or get a special light. I take Matisse for short car rides through neighborhoods a few times a week, and his favorite chair he likes to climb up, is right underneath a skylight, so he gets plenty of sun.
In terms of improving nutrition when she's picky. I've heard Eclectus's referred to as large lorikeets, which like to feed on nectar....so not surprisingly he enjoys drinking juices. Maybe you can make smoothies for her that have healthy things in it, with some fruit for added sweetness.