Somehow, I share the same email address as someone else – how do I stop this?

I have the email address '*** Email address is removed for privacy ***' - but oddly, so does a lady in Australia. I don't know how this is possible, but it's rather irritating recieving emails intended for her, and knowing that certain emails for me have gone to her (although i haven't been able to contact her as I can't email her!). Any help resolving this would be great!

Thanks