Countess Zaleska was actually a former Dracula's victim.
We know that is commonly in fiction that sometimes a vampire father is the monster that created another vampires with it's blood. Von Helsing tells that Zaleska died a hundred years ago. Maybe Dracula turned her into a vampire.Countess Zaleska is a dhampir.
Dracula attacked and transformed a woman who was pregnant, so the child born with the curse of the Draculas, half human, and half vampire. At a point, Marya remembers a song that her mother singed of her, in her childhood. Also, she clearly hates Dracula. Probably "Zaleska" was her mother's surname, or an alias.- That's why she can drink tea, also.
- Actually the novelization by "Carl Dreadstone" implied this strongly.
Countess Zaleska survived offscreen.
Dracula was killed many times and he survived. Why she not?- Probably confirmed in the novel sequels for Return of the Wolf Man, in The Devil's Brood and The Devils Night.
Lili after her death return as a vampire
