Words have different meanings in different cultures. "Slut" isn't what I'd use either, as there isn't anything sexual about her being proud of her body. Now, "narcissist" is a proper descriptor, or even "exhibitionist"fit.
Well i'm sure that in Japan walking around almost naked like the elf girl does would get you called slut and a quick visit to the police for public indecency. Doing this at a cosplay event is fine though.