Actually, I think I just realized what happened.
Rather than overcoming her desire to live up to her sister's legacy, she probably overcame the embarrassment of trying to live up to her sister's legacy.
That would explain why she ends up looking more like her sister, and it makes more sense...
This is definitely "Scar Transformation"
She must've overcome her obsession with her dead superhero sister inside of her mental space when she opened that door (which also explains why she even became a hero in the first place, but we could've already guessed that)
Idk why her overcoming that...
It took me a minute to realize why I felt like I'd seen the girl on the cover's face, before, and I realized that it's because she kinda looks like the main girl from Damedol, but with a different haircut.