Hello,
You cannot change the name of a driver because the license is non-transferable and sold individually. It sounds like she has not registered for an account yet. If you go to your name in the middle of Logbook and click the arrow next to your name, you'll get a drop download list to add driver. Have her sign up using her email, that will active the free 30 day trial for her.
I hope this information helps, please let me know if you have any other questions. Thank you and have a great day.