I am assuming that they are confined somehow either with electric fence or similar, I am just trying to establish if the henpecked hen can get away, if not give them something to do such as scratch through a pile of compost etc or hang up some cabbages, this may diffuse the situation, but it may not!
We had a badly pecked hen once, purple spray does keep the others off and the hen made a good recovery and all settled down. Also make sure you have enough feeders and drinkers at least 2 of each so that the lower orders can still get something to eat and drink without steeping on the others territory so to speak.