Re: ex-
As a result of what what some might call a character defect, I have in my lifetime made a number of proposals that have not resulted in a wedding ceremony. Perhaps one of the reasons I came into TEFL was the opportunity it gave me to flee countries at relatively short notice
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If I ever refer to the ladies concerned, I use both 'ex-' and 'former' with 'fiancée'. I probably use 'ex-' more, because that's the form I used of the one I didn't get away from until after the ceremony.
Context is always important; labelling is rarely important.