|Install the new HDD and do a clean install of the Operating System and any software you want her to have.|
Ghosting the whole drive copys everything on the HDD, Data recovery might still be possible.
You could use software such as Eraser to overwrite the Free and Slack space, which will prevent data recovery.
Even so total removal can only be accomplished by destroying the drive or replacing it with a new HDD.
There is nothing to learn from someone who already agrees with you.