ATF may in time damage pump or seal. I doubt given the time frame on your friends car from the time of addition of fluid till the time of failure had anything at all to to with it. Ask yourself why it was necessary to add fluid to the system in the first place, and I believe you will find the cause of failure. (Lack of fluid)!!!!!!. Whine is caused by air in system,such as when it is not full of fluid. Can also in my experience be sucked in around pump shaft seal.
Just something to ponder.
Simplest fix would be just replace complete pump. Pretty straight forward job. Make sure steering reservoir is full before turning over engine after replacement of pump. I usually pull and ground ignition wire and spin over the engine a few times with the starter,then refill reservoir before starting. System will self bleed if you turn the steering wheel lock to lock a few times. Be sure to check hoses connections, and steering box for leakage. Watch carefully for the first few dozen miles for leaks.
Hope this helps some.