“fiancé” was used twice. Once by the writer, the other time by the sister. I would assume that his sister would know the difference.
When in doubt, check other sites.
His sister probably did know the difference - but when speaking with the "journalist," she didn't bother actually spelling out what she was saying. Instead, she simply spoke, relying upon the "journalist" to properly transcribe her words.*
Big mistake!
Regards,
*Or what would you expect?! Sister: My brother was found unresponsive by his fiancée. That's spelled f-i-a-n-c- "e" with an accent aigu... No, no: Not "grave" - The other way! - and then another "e."