The purple comb sounds worrisome. It could be that she was getting sick when the bullying started occurring. Chickens will pick on a weak link.
I had recommended keeping her inside the coop just to keep her rank in the pecking order, but she may need to come inside to be observed closely. I would keep her inside with you to offer food and water. Is her lower belly between her legs enlarged, more than the others? It looks more full in the pictures, and that can sometimes be a sign of ascites or internal laying. I wonder why she cannot stand now? She does sound like she is sick from another reason.
I had recommended keeping her inside the coop just to keep her rank in the pecking order, but she may need to come inside to be observed closely. I would keep her inside with you to offer food and water. Is her lower belly between her legs enlarged, more than the others? It looks more full in the pictures, and that can sometimes be a sign of ascites or internal laying. I wonder why she cannot stand now? She does sound like she is sick from another reason.