What is the ruling on a volunteer being a manager in a charity organization where unlawful mixing of sexes, loud music, and perhaps usurious dealings are prevalent, and she is unable to prevent these reprehensible acts? And is it permissible for her to volunteer there as an ordinary volunteer, not as a manager?

If the work necessitates participation in suspicious intermingling and parties that include forbidden acts, then it is not permissible to continue in it. However, if it does not require that, and is limited to permissible actions, then it is permissible, while striving to denounce evil and enjoin good to the best of one's ability.