I have noticed my older hens will stay on the roost to avoid the cockerels and roosters until they molt and some time after and quite honestly, would dehydrate and or starve themselves to death if allowed to. I have to lock all the boys up to allow the girls to eat and drink. After awhile, once they are finished molting, they are fine. This might be what is happening with yours.
I didn't know what was going on all week while I was at work. Last month I had the state out to test birds and noticed how scrawny the old girls were. As soon as I put them on the floor by the food the males would attack them to mate and the hens would just scream. Somehow the males pick on these hens in their weakened state. I had one so dehydrated and light in weight she felt like air. The lab tech could't get blood from her due to that and I then figured out what was going on.
Glad you discovered the problem with yours. Ivy is pretty tough and usually intimidates the roosters. We have only 2 for over 40 girls, so nobody is really overmated. She is almost 3 years old now. I hope she stays with me for a long time to come.