Wow, sounds like quite the experience, Emmamarie, and I can relate! My Quilly went through something similar with 1 exception - he had some sort of virus that was detectable on the X RAYs, Ultrasound, and CAT scans. We still don't know - since October - what it actually was, but slowly but surely he came back to normal! He is still on an antibiotic, and will probably be on one for another 2 months or so before we try and back off and then see what happens.
What I can recommend is to feed your little girl as many mealworms as she wants to hold up her weight - I give him about 10 medium ones every day, plus some superworms on top of that. He is still on the critical carnivore care food, but instead of syringe feeding it, I make some in a bowl and he eats it on his own overnight while he is active. Maybe you can put a couple kibbles into a bowl of the special food so she associates it as good?
I am by no means an expert, but hope that my story helps you a bit!
A former hedgehog owner