So her daughter has Nephrotic syndrome. Shit I would be very worried about the cause of it. This although can be treated quite quickly it always comes with a serious condition that causes it as it is due to serious water retention caused by other illnesses most of which are quite serious especially in a young child
Somehow I doubt very much if she came home and her daughter was swollen she would have had a diagnoses that bloody quick to know by mid afternoon. The hospitals I have worked in take a few hours to diagnose as blood and urine tests are needed. If she had come home to find her daughter swollen she would have had to go to A&E which would mean it would be at least tea time before they got near a diagnoses as to start they would go with allergies whilst waiting for results then they would look at other less serious disorders as the results don't come back that quickly
If you are going to make up excuses you should at least know what it is you are talking about so you don't get found out. Why not just say she forgot?