How does Amal use a particular incident from her own past as an example of the lack of one "Muslim appearance" (135) in Chapter 13?

Amal asserts the absurdity of the fact that some people think there is one particular “Muslim appearance” (135). As an example, she recalls that the year before, when she had first started to attend McCleans Prep, one of her instructors had been shocked to learn that Amal was a Muslim. Amal remembers the teacher exclaiming, “But you have fair hair and light eyes!” (135).