My name is ***** ***** I am an experienced criminal
One way to do this would be to send an email to the stepmom -- not to confront her or arouse her suspicion -- but for some neutral reason to get a reply. Then you can trace the headers in her email and find her computer
's IP number.
Headers will look like gibberish but they give the route an email takes. Your server should tell you how to find them, because they vary from one ISP carrier to another and where to find the computer of origin among the numbers. If there's a match, you've found your person.
Of course, if she has multiple ways of communicating and can do so from different places and servers, that will not work.
You could also find a site that will trace an IP, but all you'll get is a city and country. You won't get a full address or carrier.
The other would be to just report the computer hacking
to the police and let the police use their tools to investigate and then get her prosecuted, since this is a crime in all states. If the police won't take action because they do not think you have enough evidence against the step-mother, a private investigator would be helpful.