If the hitch is properly installed and set up, you can back up with the hitch attached. I have seen poorly installed/set up hitches which can cause a problem backing up.
I suggest that your friend get the instructions on line for their hitch and read how to install and set it up.
How big is the trailer? You can safely use a friction type sway control up to about 25' or 26'. Beyond that I would use a hitch like a Reese Dual Cam with the integral sway control.
Amateur Radio Operator (KE5DFR)|Full-Time! - 2012 6.7L Ford Crew Cab Dually -2013 HitchHiker Champagne 38RLRSB - Travel with one Standard Schnauzer and one small Timneh African Gray Parrot