It works! The circle on the floor opens up after Serana adds her blood to the ingredients.
J’Zhirr wonders what Serana will do if we find her mother. It turns out, Serana is asking herself the same thing. She says of her mother, “She always seemed happy, before we heard the prophecy. Then it all changed. She become a different person. They both did.”
This one guesses that we will never know why Serana’s mother did the things she did until we find her.