Roughly speaking, the nurse saw that my wife was fat and therefore inferred that she must be diabetic. She saw the blood and assumed that my wife was suffering

Roughly speaking, the nurse saw that my wife was fat and therefore inferred that she must be diabetic. She saw the blood and assumed that my wife was suffering skin lesions from said diabetes. My wife informed said nurse about the stabbing. The nurse, like anyone who has performed tech support, is aware that people lie about what happened. Furthermore, diabetes is fairly common while stab wounds are relatively rare. She decided that the probability of my wife suffering from a stab wound and not being diabetic was less than the probability of my wife being an embarrassed diabetic who made up a story about being stabbed. She therefore stuck with her original hypothesis and worked from there.