Here is a Complaint Letter. July 24, 2005 Dear Hospital Administrator, Last month, my daughter Susan was in your hospital for three days when she had her appendix(阑尾) removed. The nurses were very friendly and I am satisfied that she received good medical care. However, there were several aspects of the service that were not satisfactory. My first complaint is the fee. We just got the bill and we were charged 400 dollars a day for a semi-private room. The TV, medicine, doctor's bill, nursing care and tab tests were all extra. That is outrageous(不合理的). She could have had a room all to herself with TV in the best hotel in town for half that. We were paying the bill ourselves and we were not rich people. Second, the room was not clean. The sheet was dirty. This is a serious concern when you have sick people. Sincerely, Mary Brown What's the relationship between Susan and the writer? They are ______.