"Costume change " is used to describe an outfit change , but when an actor is IN CHARACTER . Not when they're appearing somewhere as themselves .
There's a reason why Tiffany emphasized that's she's not in character right now and that this is her real life moment . It doesn't have to mean "Halloween costume" . It can be a regular looking outfit or gown but will be categorized as "costume" if an actor is in character on stage or in movies etc .
At the very least, the reporter needs to watch her wording. I wouldn't say it was definitely an intentionally shady comment , but it's easy for someone to take it that way when you consider the context of "costume change".
If this doesn't make sense to anyone I recommend making Google your friend really quick to confirm.
Tiff had a right to correct her. At the least, her wording was simply wrong.