Then again, perhaps it's just the Americans that use fiance for both sexes.
In Singapore, we use the dictionary definitions, both 'fiance' and 'fiancee' as well. As Wendy puts it
it's the recognised, correct English spelling (UK, US, Irish, Canadian, Australian etc) version of a word we stole from the French.
Or perhaps it's a Commonwealth thing, and US is not part of the Commonwealth. Who knows?
metwin1