Is it ethical for doctors to withdraw treatment for health issues?

She was admitted to the hospital with a severe UTI, which was successfully treated after the specific bacteria and the effective anti-biotic was identified. However, she was dehydrated and was given IV fluids, resulting in fluid collecting in her extremities and around her lungs. Even though her kidneys are functioning (creatinine = 1.3). 2 liters of fluid were removed from around her lungs last week. This week, she has developed issues with tachycardia, which then causes respiratory distress. Both cause physical and mental distress. It seems like a comfort issue and should be treated. What do you think? Is their approach ethical?