Yes, you can update your gift and resend it to someone new as long as the gift has not been redeemed and is within 90 days of purchasing this promotion.

You can manage your gift subscription directly from the settings of your account: log in your 21 draw account then go to "Account" and "Gift Cards" or directly from this link:

You will then be able to modify the sender and resend your invitation to someone else by clicking on “Manage” on the right hand side of your friend's email address.