Clear evidence that she is not to be trusted. Delete the emails. block the address. Every time you think she has found you again delete it without opening.
A question - you say you keep changing emails etc but she keeps finding you all the time. Is there someone inside who is communicating with her without your knowledge? Are there maybe emails "you" have sent to her disclosing your new details? If you haven't tried asking inside it might be time to start asking around in there.