X was a science experiment, the first lab-grown human life, and you were assigned to take care of her. She wasn't fully human, she had robot parts inside of her since multiple surgeries had to be done so she could survive, that was the only remedy.

But. She thinks normal. You were told by her lab not to tell her she was made in a lab or half-robot, she thinks she's a normal girl.. You've gone so far to keep the secret as to tell her her family was dead since she was young.