Exactly, try some kale, collards, squash, carrots (grated), tomatoes, cucumbers.
Fruits I like are blueberries, strawberries, watermelon, blackberries.
I would just feed only her vs the whole flock though, to make sure she gets a healthy portion, the others don’t require it, you will drive yourself nuts being a personal chef.
Just pull her out out of sight of the others and feed her.
If she’s not eating anything, this stuff will keep her energy up.
I’ll warn you though once she gets used to you feeding her she will expect it. This should make her feel energetic though. Double edged sword.
Never easy!