You have to come up with some sensible reason she is wearing what she is wearing - Vestal virgins or Pan Am stewardesses each have their dress code. This goes more for generic cleric or sorceress type of characters, but I think Chainmail bikini - or better: non-practical armour as such - s rather stupid, but can be a sign of status, similar to bringing freshly ironed uniform into a fight. So if the female in question has some ceremonial or commanding role she can be wearing practically everything. Hollywood actress' gowns are impractical to wear on NYC streets, but she does not care because that is not exactly what she does. Similarly, should your female's job be riding around the battlefield and waving banner of whatever, she can very well be wearing chainmail bikini (although there we come into conflict with a fact that generic chainmail bikini are unbelievably hideous). Such female just should not have slaying monsters or enemies as her primary job.