The figurative meaning of persona grata in this context suggests that Callista is a fully accepted and respected member of the student body due to her efforts and advocacy as student council president. She has gained popularity and approval among her peers for her initiative to lobby for early release Fridays, indicating her positive influence and acceptance within the school community.
Given this understanding, the most fitting response from the options provided would be:
Callista is being personified as student council president to show her power in the position.