The sword works on hate and anger. Nightingale has neither towards the MC therefore, just like initially with Finn, the sword is useless to him and he relies solely on the skills he very much lacks (to back up
RNasc4444 as you are all correct to play devil's advocate).
If he tries to rile up Nightingale or piss her off, I can't see it working, she far too canny, experienced and level-headed (compared to a brash Finn) to fall for any trick like that....so therefore the sword is just an ordinary sword in the hands of the MC against her, someone else who has far, far, far more experience, skills and swordsmanship than our dim protaganist.