I bought some stop pecking liquid and was just wondering if it would work or not. I feel so sorry for her she is such a nice chicken (Polish)
A few things could be going on here. Are all the other hens picking on her or just one aggressor? Do they all have enough space? If it's just one aggressor picking on this hen you could try splitting the bully out for awhile or putting her in pinless peepers. If it's being caused by something else like lack of space that will need to be fixed to solve the issue.