By Muad'Dib do I love this community for the continuous Dune references. *wipes away tears of pride*
However, eschewing Mentat levels of logic, some basic perception of consequence should help her avoid dangerous situations. I think some are tying fear and self-preservation too closely to one another. Fear is the most basic, animal level drive that helps us avoid danger. But even after suffering the lost of that primal driver, one should be able to use simple cause and effect to avoid even the low-conscious threshold dangers fear helps us to avoid.
Case in point, SM's mugging/near-assault encounter. General lack of fear may have lessened the gravity of the situation, but she's a higher functioning being. Where was the presence of logic in her actions? "This is an individual I do not know, beckoning me when I am alone, in a place where I am not likely to be seen. Should this individual mean me harm, I've no means of self-defense. Heeding this individual's call is unwise."
Perhaps the loss of her amygdala has lead to more than mere fearlessness, but an actual inability to comprehend dangers to her person, something with much more severe ramifications. Several of the tests they led her through: the haunted house, the scary movies, etc. Seem prone to individual interpretation, unless they were all based around acute, sudden shock. I'd be more interested in measuring her willingness to pass her hand through an open flame to reach a desired object. Something most wouldn't consider fearful, but would consider stupid.