Avast, Ye Scurvy Dog!
No matter how much the navies of the civilized powers patrol the seas, piracy is inevitable. Merchant ships transporting goods from one port to the next make all too tempting of a target once they get out onto the open water and far from help; and it's not like the average ship can afford to keep a mage on crew on every voyage just to defend against the unlikely chances they'll actually run into a pirate.
Xariah's booked passage across the sea, and has the unfortunate luck of setting sail on one of those fated voyages. Pirates run down the ship and loot everything of value. Including her. Perhaps she'll spend some time with her new shipmates at sea providing entertainment for the captain and the crew, or perhaps their intention is to take her to the nearest pirate-friendly port and sell her off like the rest of their haul. Into slavery, perhaps to be forced to work at the port brothel? You never know with pirates!