Sometimes she thinks she's not willing to die for him.
It is only a fleeting thought that appears at the most random moments, when she is doing something tedious like mopping the floor, or in the middle of eating dinner with her squad, or lying in bed, preparing to sleep. It does not come often, but when it does, she immediately pushes it away, shoves it to the back corner of her mind because it's not right, she's being stupid; he handpicked her for his squad and he is her captain, she is his soldier; if he needs her to die for him then she will, without hesitation.
But she also remembers long nights spent talking with Hanji by the fireplace, or the many times she's teased Auruo mercilessly and then mopped up his blood with her handkerchief, or the smell of freshly baked bread in the air or the exhilarating rush of soaring through the skies on her 3DMG or the feel of snowflakes on her skin as the first snow of the winter sets in, powdery and sparkling and brilliant in the crisp, chilly air.
She remembers these things, and then she thinks of her captain, cold and stoic, scowling and caustic, sarcastic and foul-mouthed, never smiling, never pleased, and she wonders if she'd really be willing to trade everything for that.
And then the guilt settles in and she forces the thoughts away, because they're not right and she's being selfish; he does care for his soldiers, she knows it, she's seen it, and she trusts him, trusts him with her life, and he trusts them too, she knows he does, and her brain is stupid, selfish, traitorous for even thinking these thoughts.
The doubt never completely leaves her though; it attacks her at the most random times and she hates herself for it.
I'm going to devote myself to him, she writes to her father, and she tries to believe it.