Thats horrible, I'm sorry to hear about what happened to your friends hamster.
The first hamster I owned was a syrian when I was young. My little sister broke into her cage one day and I came home to find my poor ham with what seemed to be a broken leg or foot hobbling around my bedroom floor.
I recall at the time a vet telling me over the phone that I could splint it on my own. But then the hamster would probably just chew at it anyway. I'm sure a veterinarian could offer the best advice. But back in the day when it happened to my old hamster I just let it heal on its own. Eventually it healed but her foot was out of alignment and she hobbled around funny. But she didn't seem bothered by it and lived out the remainder of her life.
Of course if it can be treated your friend should seek help, But if it is old perhaps pain medication can be given and the injury left to heal on it own? But then there is the possibility it could easily break again.
Well please let us know how it goes. Or else get your friend to join HC and post us updates :P