The locator spell had been mysteriously coy about this girl, so they'd known it might take Xander awhile to find her with just "the Caribbean" as a target. Willow enchanted him a compass that would always point to the nearest Slayer, but it wasn't easy to get people to just sail off "that-a-way" on his say-so; he bounced from port to port for awhile, soaking up sunshine and legends, before finally getting close enough that his destination became obvious.
The Isle des Cruces was supposedly sacred ground for the Captain of the Flying Dutchman, and thus sparsely settled. Once he actually got there, she was easy to find-- and surprisingly accepting of his tale.
"After undead pirates and sea-goddesses," she said with a smile, blond hair whipping in the breeze, "vampires rather pale in comparison."
Nonetheless, she refused to leave. The only thing that shook her composure was his compass; she stared at it as though she'd seen a ghost, then shook her head. "I have a higher duty," she said. "One with a more enduring claim."
Xander was careful to note that in her file when he left. Someday, the Council might need to know what that duty was.