Hi,
It could be a disease of some sort so you might want to research and see if her condition picks up as a symptom. Is it possible for you to move her legs, or are they stiff? This might be a strange idea and I have no idea if it has been done before but you might want to sling her up with straps running in between her legs and under her belly. That can help to give her some support and maybe get her to stand on her own so that she can maybe gain some control over her body. It is something that my dad has done with the cows out here on the ranch when they are hurt or unable to stand. I would use a soft strap, maybe bungee cords, possibly cushioned with cloth to hold her up. I have no idea if it will work but I think that it is definitely worth a try.
How old is the hen? Is she laying eggs? Is there anything that might have gotten into the coop and scared her? How is her breathing? Check her temperature and heart rate, if you can. The average body temperature of a chicken is 41 to 45 °C (105.8 to 113 °F) and the average heart rate is 400 beats per minute. You can get the temperature by putting a thermometer or other temp-measuring device under her wing. Just make sure that the temperature tool is easily cleanable. Her heart rate can be found, I think, by gently pressing your fingers under her chin, or any other area where you can find a large artery. Make sure that you don't cut it off, just press enough for you to feel the pulse. Set a timer or have someone help you and count the beats for 15 seconds. A chickens heart rate is really fast so it will be hard but a rough estimate should be enough. Multiply the number of beats by 4 to see what the final beats per minute is. That information should help to decide what is wrong.
I don't know about the bad odor. That is strange.
Your hen could be stressed, sick, or something else. I will keep checking on here so keep me updated.
Hope that this helps!
~chickenchick
