What exactly was the artist going for when they drew this face? Is it anger? Fear? Joy?
Defiance? Defiance, fear, or anger towards what? Maybe the dentist just asked to see her molars, but she thought she couldn't open her mouth to show them? Perhaps it is one of those strange expressions that does not exist outside of animation, and thus is implied to be the result of an emotion unknowable to us real lifers? We may never know.