I love my ex and she has an online relationship with someone online what can I do?

My ex and I have a child together but we have been broken up for about a year. And now she is talking to someone she has never met before online. The guy lives in Australia and we live in west palm beach Florida. What can I do to get her to want me again. We live together and we get along fairly well... I mean at times she is mean sarcastic, short and punchy with me but then there are times when she is nice. What can I do so that she stops talking to this person she had never met before? I mean I still love her as you can see... But it bothers me that someone millions of miles away is getting her attention and I'm 5 feet from her and nothing.... What can I do? Thanks