Answer:
The theme of "I Am Not Your Perfect Mexican Daughter" is secrecy and lies.
Explanation from litcharts.com to better understand the theme:
As the novel unfolds and Julia digs deeper into the secrets her recently-deceased older sister Olga left behind, she comes face-to-face with more and more unsettling truths about her family’s past. In the end, Sánchez ultimately suggests that some secrets are too painful to share—and that some lies are actually a mercy, meant to protect people from hurtful, devastating truths.
P.S: Why do you want me to report your questions and answers? Unless it is something that violates the Honor Code, I am not going to do that