Welcome to the Asana Community Forum @Gordon_Moe!
In this case I actually recommend reaching out to Asana Support so they can help to change her email.
Alternatively you can remove her old user via the admin panel which will then create a project with all tasks she had assigned and this project can then be reassigned to her new email. She would however not have all the previous access to projects, teams, tasks etc so support is definitely the best option in this case.