In the book "Staying Fat for Sarah Byrnes" by Chris crutcher, what happend to sarah byrnes during her childhood? How did she get the scars on her face?

Sarah Byrnes was burned as a three year old, supposedly when a pot of spaghetti fell on her. However, when told that her father chose not to have the scars repaired because they would make her tough, the reader begins to wonder if Sarah Byrnes' father might have had something to do with her initial injuries.