That's kind of my point. Orihime's powers have been shown to have limits, or @ least things she hasn't done so far. (Correct me If I'm wrong, my mistake) but Orihime reverses the damage on the body, and we have never seen that done when a weapon was still in the body. She doesn't or can't just reverse the weapon and wound away. She can't even revert a weapon into nothingness, apparently seeing as she has never done it. Also for instance, why couldn't she just reverse Ichigo's powerless state back to before, @ no point? No doubt she's powerful, but she does have limits, so far anyway.
The way I see it, it is possible that the ability to "hear" that Yukio canceled out referred to "everything". In other words, Orihime can heal anything but if it's too quick a shot @ too vital a point, (especially perhaps on her self), then it would be like if some1 stabbed her in the head in the part of her brain that controls her abilities, and left the weapon there. That's how I see this situation might be explained. She might be "willing" all she wants, but if her will cannot connect with her ability to use and control her abilities, then it all still means nothing, and her powers would never activate in the 1st place. They would never activate Regardless of if she believed in her abilities or not. Thus the earlier muscle analogy.