[name]Kaiya[/name] may not be the original spelling of [name]Caia[/name] but I think it is equally understandable in romanji and English, matches [name]Audrey[/name], and is pretty straight forward. There is no “Japanese spelling” using English letters, only hiragana, katakana and kanji, so this is as close as it gets. The spelling [name]Caia[/name] was the [name]Roman[/name] goddess of fire, so there is that connection to romanji.