Number One (MHA x reader OC)

Miriun Takami. Does that name ring a bell? Once upon a time, it would've. But that was a long time ago. Now, the label that you would recognize would be... 'Keigo's little cousin'.
No longer number one. Now she was second best. Her name was forever to be tied to Keigo's. Always second. Never first.
During her childhood, she hadn't even known about her ''amazing cousin'. Or, she had- he was the third top hero, after all, as she is reminded practically every day- but she hadn't known they were related. Miriun's future was bright; she was sure to be a star. And then, one fateful day when she was 8, her parents mysteriously disappeared. She was sent to live in Japan, with her wonderful cousin Keigo. Number One.
Miriun is sick of being Number Two. Of being 'just Keigo's cousin'. Of having to hear 'when Keigo was your age...' every time she thinks she's finally done something to show she's strong, just on her own.
But it seems there are only two ways to be number one... Either become the best hero she could possibly be, surpassing even All Might... Or become a villain and takedown Keigo once and for all.
When the two choices are presented to her on a silver platter, which path will she take?
What would you do to become Number One?