In "My Nerdy BFF Left Me Once I Became Popular," the narrator reflects on how their friendship with a once-close, nerdy best friend changed after they gained popularity. As the narrator's social status increased, the dynamics of their relationship shifted, leading to feelings of betrayal and loss. The story explores themes of friendship, identity, and the impact of social hierarchies on personal connections. Ultimately, the narrator grapples with the emotional fallout of their friend's departure and the price of popularity.