If she doesn't get nutrition she will die.
The vet should be able to teach you how to tube feed her but I'm afraid it's just too late.
I highly recommend getting a necropsy so you know, for sure, what the problem is.
Are you in the US?
This looks bad...(not sugar coating here). This is more than likely a bacteria infection and NOT Coccidiosis.
It may be too late to help her with antibiotics but if a vet visit is doable for some antibiotics then I'd take her now.
Welcome to BYC.
I am going to ask that this post be moved to the emergency section for you.
Can you move her away from her friends immediately and take a video of her?