Gender blender

Her father wants to make her younger sister successor
He sent her to war, being dismissed bc he's a woman
6y later, she figured out the enemy's plans, no one listened
captured, named herself Paul to die a knights death, not raped
The king figured out she was a woman...

Her brother is missing, came back pretending to be him
She gets justice for everyone who has wronged him
The president of a big company becomes her lit tutor
They become very close, doesn't know she's a girl
She lived in Europe, also pretendented to be a guy there
She is the muse of a very famous fashion designer LW