Despite being taken prisoner, Kurisu was adamant that her brother would come for her and kill the pirates that took her, though the pirates themselves didn't believe this. However, as the pirates sailed near Hindarsfjall, a storm struck and, taking advantage of the chaos, Kurisu jumped overboard.
She nearly died though from her injuries but thankfully for her and the others onboard, priestesses from Freya's temple found the shipwrecked group and tended to them. She then spent a couple weeks recovering at their temple before deciding to head back home as her family must be worried about her.
If Geralt talks to her: Kurisu informed Geralt she was heading home to Blandare soon.