Yeah there's no way he would guess unless he saw her back or something, bc none of the droids in SW are even close to humanoid looking. And it's considered best practices to wipe their memory when they develop too much of a personality. He'd find her absolutely fascinating, no matter how he finds out. I do like a good comedy of errors so we could definitely play with how long can this go on before he figures it out.

Also B2EMO is the cutest little thing. An Imperial officer kicks him over and it sets off a riot in Cassian's hometown lmfao