Is it possible to terminate hack in process?

Sorry, I was in a panic and actually wrote out my situation in the title! Oops. To recap, Got e-mail from relative and opened it only to find it to be bogus. Deleted it and wrote new e-mail to relative to tell her she had been hacked. Received an e-mail in response-from her address-from the hacker telling me it was "not a hack" and she needed money".  Called relative to explain what had happened and she has not been able to log into her e-mail or facebook account. She thinks that since I opened the e-mail the hacker may be taking over my account as well. She cannot access her distribution list and said she needs to go to Apple in person to get help. What should I be doing to block this?