Is it obligatory to advise a woman who displays uncovered pictures of women, or a teacher who wears tight trousers in front of women, despite her fundamental immodesty?

The principle is to prioritize the most important matters in enjoining good and forbidding evil. However, this does not mean refraining from forbidding a lesser evil if the perpetrator is also engaged in a greater evil. The obligation is to enjoin all good and forbid all evil according to one's ability. If it is impossible to combine both, the more important takes precedence. If enjoining the more important good or forbidding the greater evil becomes impossible, the duty to enjoin or forbid other matters does not fall away, for what is achievable is not forfeited by what is difficult.