I feel your pain. My gelding is on 2 mg Prascend daily, and he has had a definite decrease in his appetite. However, he is also extraordinarily picky, so even when he WILL eat, he only likes certain things. He’s 20-ish and on the skinnier side, so he NEEDS to eat.
A muzzle has helped tremendously. When he wears it (they tend to go “missing”), he has a better appetite. APF has also helped curb the side-effects from the Prascend. So does time.
What works best for him is changing his food often, but ever so slightly. He eats better when he has something different in his normal mix. He doesn’t eat a LOT (I’m lucky if I can get him to eat more than 1 lb per feeding), but he has been eating most, if not all of his food… including his pills! Since he decided he doesn’t like TC Senior right now, he’s getting Pennfield Fibergized and TC Light, in addition to Buckeye Grown N Win. And he gets an alfalfa mash for lunch.
None of the other supplements helped with any symptoms. He still needs to be clipped multiple times a year, though he eventually partially sheds out.
I think your plan is a good one. Take her off the Prascend if she isn’t responding well to it. Manage with low NSC feed, grass intake, and exercise. She may surprise you!