You have a combination of online stalking and/or identity theft. These are crimes, report them to your local police agency.
They will investigate, and depending on what they uncover, they may forward their findings to the county prosecutor, who may decide to file charges or seek an indictment. That she is in Australia only makes it more problematic, but if your case is serious enough, that won't stop them.
Additionally, if you have and existing and ongoing divorce proceeding in court, you could bring this issue up with the judge, and ask for orders prohibiting this type of behavior.
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