If you have not already done so, configure your spam filters to block emails from her address. If that does not work, contact your email provider to see if there is a way to block emails originating from the person's ip address.
If these steps do not work, then contact your local state's attorney's office and ask them how to go about filing a statement of charges. Although the office will not provide legal advice, they should be able to tell you how to file charges.
In addition to the criminal prosecution, you may want to file a civil lawsuit for nuisance. State laws differ on the interpretation of this particular tort, so you may want to at least consult with a personal injury attorney to see if you have sufficient grounds to prevail on the claim.