Her way is actually safer because your truck's camera system uses top-view to secure the perimeter around the trailer before the computer system in the truck will allow the trailer to be backed into a spot using trailer assist.
Doing it manually like you like to do Bob, technically requires a 'spotter' behind the trailer to ensure there are no obstacles or kids in the way.
Trailer assist will not allow the truck to even move in reverse if there are obstructions in the way as determined by the trucks camera system... even behind the trailer.