Helga Ruvak

Helga is missing her ruby necklace, a gift given to her by Strahd when he mistook her for a reincarnation of Tatyana Federovna. However, she has since fallen from his graces and he took away the necklace only to give it to one of his other brides, Anastrasya von Zarovich. Helga is bitter about being sidelined like this and incensed at the other bride flaunting her treasure.
When she first encounters the characters, Helga pleads with the them to help her get the necklace back, claiming it to be a family heirloom. She knows where Anastrasya von Zarovich keeps it (in her crypt in area K84), and wants to see her dead. In all Helga does, she presents herself as an innocent human woman, wronged by Strahd and his minions.
Helga will still betray the characters if an opportunity to ingratiate herself with Strahd presents itself— she wants nothing more than to be in his good graces again. There is a chance the characters become wise to this with a successful DC 17 Wisdom (Insight) check from how Helga tries to imitate the way Tatyana dressed and carried herself. This check can be made with advantage if they have seen the painting of Tatyana in area K37.