Pam, it worries me a lot that she is still stalking you. Sadly, I doubt that the police would be of much use.

You could take out an Apprehended Violence Order (AVO) against her. An AVO is for the courts to decide (the police are not involved). The court could rule that she can not contact you in any way nor approach you house within (say) 500 metres. There are probably Legal Aid people in Perth who can help with this. Breaking an AVO is a crime.

As far as the stalking e-mails are concerned you could contact Gmail, asking them to block all messages from her e-mail address. You would just have to say that you are being stalked. I have never had to do this but I think that Gmail is good about this - the messages just get bounced back to the originator address.

This might contribute to her psychosis (not unknown with people with BPD) but that is her problem, not yours.