Board Thread:Dark Souls II/@comment-2.223.169.191-20140325204725/@comment-1855630-20140428065439

It could be that her soul was so strong that even after being consumed by the Lordvessel there was still a fragment that could wander the world and eventually influence the person who would become the Lost Sinner. AFAIK that's the prevailing theory - the Lord souls keep exterting their influence over the land in every Link cycle.