Dunno...not a linguist. All I know is that, with my American backwoodsy drawl, "Aerith" sounds as sublimely stupid as "Argath Thadalfus." As far as appropriate usage, either gets the point across.
Yes, it was definitely a mistranslation. Kingdom Hearts is correct calling her Aerith.
No, it was NOT a mistranslation, and Kingdom Hearts only called her Aerith as fanservice.
I'm really indifferent on the matter.
*Poll Option Under Construction*