I read this story in a sf anthology in the 80s, but it could be from the 60s or 70s. It takes place centuries in the future, and the narrator is a woman who has been assigned to help a recently unfrozen 20th century woman acclimate to her time. She discovers that the 20th century woman is a complete monster with the ability to dominate others. It turns out that before the cryonically frozen were revived, they were all possessed by aliens or something, who are now free to enslave humanity.
That's Tanith Lee's "The Thaw". The unfrozen woman is named Carla Brice, and the descendant looking after her is named Tacey Brice. Tacey begins to suspect that all is not well when Carla eats her house plants, and Carla's true nature is confirmed beyond all doubt at the end when she eats a man with whom she has started a relationship.