I'm going to go out on a limb here and say she's not austistic, she's psychopathic. She clearly understands what "right" emotions are, and can feign them quite well, but can't feel them herself; that matches psychopathy, but not autism, where she just wouldn't understand emotion in general and wouldn't be so good at acting. And most importantly, after looking at MC-kun's gut instinct around her, take note that autists may be creepy, but aren't scary.
Psychopaths are.