Look, it's a fine book, okay?
There's nothing hugely wrong with this book at any point. It has all the right elements...I can't remember the heroine's name.
I remember her sisters' names. And the boy the family had more or less adopted. But the protagonist is just so...so....
Some men are born great, some achieve greatness, and some have greatness thrust upon 'em. This one got handed greatness in the Great Cosmic Destiny Lottery, and wasn't even paying attention at the time, being much more interested in her own inner feelings of inadequacy and Being Left Out of Greatness.
That's just her prestige. Her personality, sadly, barely gets up to 'mediocre, in an adolescent, mildly self-absorbed sort of way.'
Sigh. I cheered when she started swordwork, hoping that the heroine would finally -- finally! love something or strive at something, find a reason to push herself, to be grateful, to be fascinated, to work at it. I saw none of that, just: "...and she totally liked it, at was naturally way good at it (this from a girl with manifestly no athleticism, coordination, discipline, staying power, or any known abilities of observation or reflexes? Tell me she loved it so much she overcame her weaknesses!)...and it was like, way nice to actually be good at something." She didn't fall in love with swords. She didn't break a sweat. Certainly no blood or tears contributed to this process. And other than having checked the box of 'skill attained', we never see thought, enthusiasm, or care going into it again.
And that's when I gave up on the character. Even the sword thing was just a nice brief break from her being whiny, and a setup for the future.
She eventually drifts, navel-gazes, and is pushed (at one point literally) into 'greatness'.