You could use that logic to say that no character is poorly written.
Shallans personallity is literally whatever works for the scene and that's it.
She says she doesn't like confrontation in book one and that seems to be the case, She hid from Jasnah, and froze from the theives in the alley
Yet the next book she becomes James Bond with an adtitude, she throws verbal insults at everyone, sneaks into high security orginizations and outmanuvers people who manipulate nations.
Then book three comes along, and she's useless!
And even worse she is inconsistanct even in the same book, In Oathbringer she gets outplayed by an assitant spy after doing the same thing to a full Ghostblood? Are you kidding me? and then she is in one scene subverting the entire nobility and the next she falls apart.
There is a dissonance there and it doesn't work well, it could be played like a spy with a soft side but it's played like a pappered noble with a secret side, and for those of us here that just doesn't work, especially the way it's played out.