Suzanne,
Since she already has a private profile where she is shown as "Living". If you are the manager you can go to the "Edit" tab and enter her email address. That way WikiTree will automatically send her an invite to join WikiTree. Once this is done, then you can follow what Ros said. You can assist her in doing the entries as needed, but because of the privacy issues, it must come from her. Only the living person can enter their own DNA test information on their profile.