You would have to separate her away from the flock part time if you are free feeding them. Do you know what breed she is? Is she fat all over, or does she have a big abdomen?
Feed only grower/finisher if they aren't laying. Only layer feed if they are all laying.
Feeding scratch, which most people do, in excess can make them fat.
Re-write:
She is a Rhode Island Red and very overweight. She sleeps on the floor at night and can't hop on roost. She has got a big abdomen. Please help.