You are right. They thought she had it because of her low potassium. In bulemics, the throwing up causes electrolyte imbalance and drinking alot of water makes it worse. They just supposed it. And suddenly it was fact. Odd thing is that she had lost weight over a period of years and was not underweight. And bulemics die from cardiac arrest, remember Karen Carpenter.
Before it was removed even the Terri Shindler Shiavo Foundation website had mentioned she had suffered from the eating disorder. From what I understand from court papers one of the basis for the lawsuit was that she was not tested by her doctor.