I'm not sure what to tell you. I hope someone else jumps on here with some ideas! The "crackling" sound almost sounds like she might be dehydrated. When did she last eat or drink on her own?
Perhaps more information might help. When did she last eat or drink? You say she is very small; do the rest of the flock let her get to food and water? Is she drinking now? I don't know, I'm just thinking more information might help.