Has she possibly had access to anything toxic? Fluids leaking from vehicles, pesticides, anything rotting or spoiled, moldy feed, etc? If you think that may be the case then activated charcoal can help for organic toxins. It's very dehydrating so you have to give a lot of fluids as well. If you want to try that it's 1 tsp of activated charcoal in 8 oz of pure water, dose 6 - 8 times a day, as much as you can get her to take (you may have to tube or syringe it). Give plenty of plain water as well in between.
For supplementing I would get a b complex tablet or capsule or a super b, and give her that once a day. Just put it in her beak and push back, she'll swallow it regardless of size. I would work on getting fluids in her regardless of whatever else you try. Don't worry about food just now, just get fluids in her. Give them room temp to slightly warm, not cold.