It might have been a bit hypocritical of her to even ask. She knew for a fact that she would have been much more hesitant to let anyone touch the sword that Arthur tended to let her "borrow" (read: she took or guilted him into letting her use). And it had nothing to do with the fact that Arthur would strangle her if she let anything happen to it, and everything with the fact that she'd have done much more to the person than strangle them if anything happened to it.
A small flash of surprise showed on her features when he said yes, and she gave him a quick, grateful smile. Morgana took it in hand. She'd never seen anything like it before. It was splendid. She held it up for proper inspection. She was just wrapping her slim fingers around the handle, when it disappeared from her grip. Just like that. Her wise widened in surprise for a second. She hadn't thought of making it disappear. And likely it would have just exploded in her hands of if she had. When she looked back towards Riku; however, she saw that it had returned in his hands. She pursed her lips slightly. Irritation over the fact that she had almost lost it, rather than at him. Irritation that melted quickly. "Very conveniant." Morgana said. "It's a beautiful weapon. I've never seen anything like it before." And Morgana had been around weapons all of her life. Her father had been a night of the realm. She was ward to Uther Pendragon, oft described as a warrior king. Even with his forbidding her from practicing with Arthur anymore, even he had never allowed her to in the first place, it would be very difficult (or she had to be thoroughly oblivious) not to know even a tiny bit about weaponry.