Here's why:
* Polyglot means a person who knows and is able to use several languages.
* The sentence highlights the aunt's fluency in three languages and her profession as a translator, directly indicating her multilingual ability.
Other terms that could be used but are less precise:
* Multilingual: This is a broader term encompassing anyone who speaks more than one language.
* Linguist: This term refers to someone who studies languages, but doesn't necessarily imply fluency.