Well, the swelling of the abdomen and especially the vomiting is a sure-fire sign your daughter has
peritonitis, which can be a complication of appendectomy. In her case, this peritonitis is when an infection from the appendicitis has developed and spread following surgery. At this point, the surgeon MUST IMMEDIATELY drain the infected abdominal fluids, drain the abscess that developed, then disinfect the abdominal cavity, and give antibiotics.