Hi @Tiffany_Schmid , before you try support as @lpb suggested, can you check whether you have the ‘Admin Console’ as an option in the dropdown menu of your avatar/profile photo in the top right.
If so, in the Admin Console, go to Members, change the filter to Guests, find the user and deprovision them from the … overflow menu on the right of their name. This will do it ‘quietly’ without sending them any notification.
If not, then contact the Admin(s) of your Asana space to do it for you.