Final answer:
Anna is experiencing the 'imaginary audience' aspect of adolescent egocentrism, where she believes others are overly focused on her appearance.
Step-by-step explanation:
Fifteen-year-old Anna is experiencing the imaginary audience aspect of adolescent egocentrism. This concept refers to an adolescent's belief that they are the center of attention and that others are as preoccupied with their appearance and actions as they are themselves. It is part of the normal developmental stage where teenagers may believe that everyone is watching and judging them, akin to an audience watching their every move. Anna's concern that her peers will negatively notice her bad hair day is a classic example of feeling that there is an imaginary audience focused on her.