Vasilka is a flesh golem created by the Abbot in the hopes that she could be the bride of Strahd, and that this would make Strahd happy.
Diath possessed her body for a short time and gave a very convincing speech. It became very clear that the Abbot was attracted to his creation.[1]
When the group returned to Barovia, Paultin was supposed to marry Vasilka.[2] The group saw that she had a new head. It was Ireena's. Mordenkainen may have destroyed her with Bigby's crushing hand.[3]