[HeartsOfFire]

Spoiler!

Intriguing! I didn't go that route. When the Arishok mentioned the artifact, I was given the option to say 'I know where it is,' but I had a feeling that wouldn't end well for Isabella, so I ignored it.

Suffice it to say, I never saw her again for the rest of the game. I just assumed her departure was a scripted event, either by her death at the hands of Castillon, or by her taking the artifact and Jack Sparrowing away.