Bianca isn't alone in what she 'should' be able, but can't. Rey should be capable of sensing others like her. Synthetics. She had felt IV's presence during her brief visit, but no one who has ever fit a similar bill from elsewhere. It reinforces the idea that there really isn't anyone else like her, much like back home. She's alone in what she is, so much so that even IV wishes to rip Rey apart, see what makes her tick.

She frowns, thinking about this and shaking her head. "Don't think this place operates under the same rules as they 'should' be." Her mouth tightens into a straight line, uncertainty etching on her expression. "If it's​ any consolation, the gods do need us. They wouldn't have been able to get anywhere without our help."

It's that mutual reliance and benefit that keeps Rey from grinding her teeth too much over the idea of being 'captive' in this place. In any case, she's used to a lack of freedom. Who is she to get offended?