The Villainess is the Heroine's Biggest Fan

When a high school girl is reborn into the world of her favorite novel, she’s ready for a life of riches, romance, and a front row seat to the drama. The problem? She’s been reborn as Mary Bell, the villainess of the story!
To make matters worse, she’s cursed to continue speaking like the original Mary Bell. Every word she utters sounds rude, conceited, and cruel. However, just as she decides she’ll need to live quietly to avoid her death flags, the original heroine of the story, Aria, gets bullied right in front of her. With no choice but to step in, Mary Bell decides to make the most of a new, unexpected proximity to her beloved main character and singer—as her sponsor!
Taking knowledge from her previous life of idols and talent agents, Mary Bell helps Aria traverse a world of nameless troupes and mediocre male leads to become Under a Beautiful Melody’s very first popstar, all while avoiding the pitfalls of the original story!