Need help in locating the person who sent email out in the name of my wife

How do I TRACE back someone who has used my wife’s email and sent email to all her email circle friends claiming that my wife was writing them from London where she is on business trip and needs them to send her $2000 via Western Union to an address in London ?

But the email has my wife email address as ” from” and for reply to ” they stated a wrong email address of my wife ”

SO, MY QUESTION IS HOW DO I TRACE BACK THE EMAIL TO ITS ORIGIN WITH THE NAME AND CONTACT INFO OF THE SENDER WHICH IS NOT IN THE EMAIL SENT ?

And how is it possible for someone else to use her email address to do that ?

Email me your answers at AFRIKALION@AOL.COM and thanks for your help

Prof Afrikadzata Deku , Docteur d’Etat, PhD