Final answer:
Based on Elah's strong emotional connections, shared identity, lifestyle influence, and long-term friendships with the group members, she is part of an in-group.
Step-by-step explanation:
The scenario described indicates that Elah is a member of a group that is very personal and significant to her and the other members. This group has influenced her lifestyle, including diet and exercise routines, suggesting strong emotional ties and a shared sense of identity among its members. In sociological terms, this type of group is considered an in-group, which is a group with which an individual identifies and feels a sense of belonging. In-groups often share common interests and support systems, and their values and norms can heavily influence the behavior of the individuals within them.
In contrast to Elah's situation, an out-group is a social group with which an individual does not identify. A secondary group is larger and more impersonal, often task-oriented and with limited emotional connection, while a formal group has a structured organization and officially defined roles and goals. Based on the given information, Elah is indeed part of an in-group with her friends from high school.
The final answer: Elah is a member of an in-group (A).