If a male sees a mumeenah with revealing clothes, (of typical western standards,norms), under what conditions must (wajib) or should (mustahab) advise to dress differently?

Also, under what type(s) of circumstances would an "excuse" be present, so to not mandate forbidding?

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If you know that you can give advice without being in a position of being humiliated then go ahead and do it with maturity and wisdom