Lili died bitten and almost bleed out by Marya who feed on her, a vampire. Probably she leaved that hospital as a vampire. Another vampire loose in London city. With Lucy/The Bloofer Lady being probably also a vampire since she was never destroyed in the last movie, we have two vampires free on London...
The novelization by "Carl Dreadstone" actually a pseudonym have a little but significative detail. In a scene, before met with the Countess, Dr. Jeffrey Garth see her paints, and make a psychological analysis. The paints revealed dark thoughs, but also a trauma with a man, very possibly her father. Now, in both the movie and novel, we don't see Marya's mother, except when she believed she is cured after burn Dracula's body, and she remembers her with joy, in very contrast with the clearly hate she feels for Dracula. The novel implied strongly by Von Helsing that Marya's mother was human. And we don't see her never. Try to don't think what happened to her. It's possible that she was killed by Dracula or Marya herself in an uncontrollable thirst attack. In the best of cases she died years ago naturally by aging.
Shortly after burning Dracula's body, Marya says "I can live a normal life" almost singing like a young girl. Her attitude remembers Sandor the frightening likeness with a senile woman that pretend to be a little girl. He knew that it didn't work.
In relation to the paints, Garth's analysis have Marya traumatized with her father. Once you know who is him, yes, the most feared vampire but also a former ruthless tyrant, a sadist who is said by Marya that his master was the Devil himself, the implications are terrifing. That would explain in part alongside with her wish to be human, her coldness, her sad but ruthless personality and her look visibly tired. What did Dracula to her?
This is both sad and ''terrifing'' if you consider Renfield (2023) as a distant sequel, and Dracula's violent, narcissistic and manipulative personality in that movie...
