The mystery girl (at least still mystery to the characters) threw that curve because there really is no sense in hiding her real last name. It is not the name, nor should it be, that causes the reactions but what the person does themselves. I know that may have messed up some things planned for characters to do, but there is a certain reason for the theatrics. Think back to when, suddenly, Harry Potter was the unexpected fourth name selected to participate in the Tri-Wizards tournament... or in fact revelations of any unknown thing in the early stages of any saga. I am not trying to through a monkey in wrenches, rather role-playing a recently-turned eighteen year old girl who has after a time decided to own the truth of why she was every conceived, let alone born, is all. I hope that explains why she is going last.
(Also, please remember, owning a truth and living up to it are two entirely different things.. that is all.)