|They'll probably never be as soft as they were when you first used them. Over time diapers lose surface fibers which makes them feel rougher (like an older towel for example), I'm afraid there's not much to be done about that.
That said, it is possible that there is a build-up of detergent and minerals that could be causing them to feel rougher than they would otherwise, especially if you or your friend have hard water.
I would try washing them again with plain hot water. If you have hard water I would add a water softener like Calgon. You can also try a vinegar soak if you'd like before the plain hot washes. Soak in water and lots of vinegar (minimum several cups, maybe even the whole jug!) for a few hours, the acid will help dislodge the mineral/detergent build-up. I'd put them through at least 2-3 hot washes to see if it helps. If during the last cycle you still see suds (pay particular attention during the hot wash part of the cycle, the hot water helps 'activate' suds more than cold) then keep washing.