Sometimes the best thing to do when you can't subvert is to double down; make you're Alchemical think of selfishness like a religious fanatic thinks about sex: i.e. it's evil and shameful and wrong and no one feels it but me! You said it yourself: they have an insular communist nation above self state and she is one of their greatest paragons. She has literally been made for a higher purpose, how can she think about such base things as her own wants and needs?! Can she verbalize this schism to another Alchemical or will they consider her a failure? From this delicious soup of suffering you have two directions you can go: A) The Ketchup route: Her motivation and purpose in life is to abolish selfishness as a means of convincing herself that she was right and to silence her nagging doubts, or B) The Hedonist route: She secret enjoys selfishness as the ultimate forbidden fruit, because it's so verboten! But she can't let anyone know... she can't let anyone find out. If that means silencing a few witness or Macbething then its something she'll ahve to do. Good thing she's the stealth archetype, right?