I could tell you of her personality, but that would spoil her route, so just keep this in mind: a sadistic girl needs to find the mc interesting enough to decide to keep him with her and alive. What increases Nyxmay's interest for you is being a different "toy", unlike any other she had so far. Choose the options that a regular tiny would not choose being with her; the mc has to survive a game? keep your head cool and advance without using extra energy. You see a weak person about to be attacked by a wild beast? try to help the weak in any way the mc can think, Nyxmay is intrigued by your bravery, and also apreciates that you have a kind heart (you will understand why later). She is playing too hard on you? do it the way she asks/wants you to do it, maybe you can enjoy it even more than any sane person despite the pain, to her surprise. And so on
Of course, always keep your manners and never disobey, that's a "must do" if you want to survive in Homaespernia