The person who born after the transplantation is neither Marry nor Julie: this means that the person after the transplantation doesn't belong to anyone of them. Brain is the central point of any person which enables him/her to act in any situation. It posse's more than single quality which can all be used in a single situation, this is all in the mind of Julia: different thoughts, different feelings, memories and Intelligence.
But now her brain seems to be a new existence, she is now living with a new persona and with a new identity. It is the human nature, ...