Can a person face criminal charges for pretending to be someone else by hiding his/her identity via false email

I live in the suburbs and have been recently talking to someone via email. A few things have made me suspicious but I have just let it go. I recently found out that this person, whom I have never met (supposedly), is actually an ex and someone who I had told not to contact me. I posted a question on an on-line forum asking for some advice. I got several responses but this person continued to talk to me long after my question was answered. My ex used to go into some of her friends and former friends email accounts just so she could see what they were up to so there is a history. Now she is contacting me via a free email account and pretending to be someone else. There has been nothing threatening but it is someone I told to leave me alone. What recourse do I have?