Absolutely. However, it would help to have proof. If she is sending you e-mails, print them out and collect them. Also print out any IM/ online messages you get. also, if she has myspace/facebook pages with anything bad about you or posts on your page, print those out. all of this is enough to get a restraining order on her. This order also includes virtual interactions. So if she continues to harass once the order has been made, you can then press charges and have her arrested.
Good luck