She has to be careful about withholding her rent for whatever reason but does the landlord manage the property or the letting agents? If the letting agents manage the property then they are responsible for contacting the landlord and putting the matter right. If the landlord is mangaing it then they will be responsible directly. From your post, Is sounds as though the letting agents are managing it which is totally down to them, go to their office and cause an absolute storm, say you are contacting the owners (bluff) if they don't do anything quickly and also the council as it is unsafe etc. BE careful about repairing it yourself as the owners could come back to you later saying it has not been done properly and retain some of your deposit. You need to keep on and on at the agents. Are they members of ARLA? If so, you can contact them and put in a complaint.