It isn't true that being on chick feed would result in poor nutrition. Quite the opposite I think it's superior in nutrients. It has more protein to support feather and muscle growth. They only thing it is lacking in for birds that are older... and even then I mean laying... is calcium. Which can be provided on the side in the form of oyster shell in most cases. It does usually have 22% protein. Which might be more than you prefer long term. But I have seen some "starter" feeds with 18% even. Hate the misleading labels but agree they are meant to be guidelines.The green poop could be from poor nutrition, as she is on chick feed that only has proper nutrition for up to 16 weeks of age.
I too feed flock raiser with 20% protein and oyster shell on the side to my whole flock.
The longer you wait the less chance of recovery for something like paraysis. I don't think that's your real issue unfortunately. But did you find any B1 or B6? Any chance she has a tick on her somewhere?are looking for vitamins.
Hope she pulls through.
Is she still eating and drinking? She might love a little scrambled egg! Good nutrients there and easy to digest.