Sisbell's power is so OP, even she doesn't realize how powerful it is. Even with her timid temperament, she's way more competent than Alice, who relies on the world's dumbest maid to be the brains of her operation.
Also, not that it's anything new, but I'm disappointed in the MC. Even if her offer was something he couldn't agree to, he really ought to have thought of a counter-offer instead of just shutting her down like that. If nothing else, it was a chance for him to solve the captain's shoulder issue and slowly work up toward something bigger.