Oh dear, poor Lil
. Pecking order can be very fierce in chickens. You may need some purple spray (yes it is called that but is actually Gentian Violet) if they are drawing blood. Hens are attracted to the colour red and would just keep pecking at it. It also acts as an antiseptic.
It may also be worth checking on what I call the usual suspects.
If she is losing feathers it may be because she is moulting. This also seems to make hens feel rather grotty. Are there lots of feathers in the coop?
Have you checked for red mites and lice? If she does not want to go back into the coop it may be because of that.
Have you wormed your hens recently?
If it is pecking order you may need to stand back and let the girls sort it out for themselves. They can get quite nasty but standby with the purple spray!
Someone more experienced than I will be along with more advice. In the meantime good luck and keep us posted!