"I'll help you," Chuck said, reassured by his grin. She was intrigued to see how well the automail functioned, which took away the last of her reservations about it. It wasn't pleasant to hurt him, but it was obvious that it was a necessary pain in order to have functional limbs again. That was worthwhile, and she didn't want to chicken out of helping him.
So with renewed confidence, she bent to pick up the leg, and after warning him ("Ready?") she helped him set it back in its place, and turned the screw to keep it in place. "There," she said, and sat down on the bed beside him as she watched him adjust to having his limbs back. She didn't know whether he would need any more help, or not, but curiosity kept her there anyway.
After a few moments, she dared to ask, "How did you lose your arm and leg to begin with? If you don't mind me asking."