I think I've said it before, but I've always figured Tamaraneans think excess clothing is provocative- you wear enough to not bounce painfully or get too personal with other people's sofas, sure, but anyone who goes around gratuitously covering themselves up obviously wants to get people speculating about what's under the clothes. Why else would you want to do that? The Titans tried to explain the Earth take on this to Kory, who was skeptical, since anyone could see that Dick and Donna had started out in nice age-appropriate costumes and slowly graduated to sexier outfits as they got old enough.
Hence, Blackfire's wearing their equivalent of the supervillainness bikini while Kory's continuing to dress in her modest, appropriate hero-wear, admiring Diana's professional fashion sense, and stoically trying to take Batman seriously. (She just can't believe he wears that in public!)