The rules say that when an elected official is unable to perform her duties, she is supposed to be replaced by someone who can. In the case of a Representative, the governor of the state is supposed to appoint someone to fill the rest of the term, and then a regular election will determine who gets to serve next.
But in this case, due to emotion the Republican governor of Arizona waited for Giffords to resign. From the time of the shooting to the time of her resignation it was clear she was unable to serve as a Representative.
I'm moved by her tragedy and amazing recovery, and even more moved by the deep love her husband has shown. But this breach of common sense and protocol bothers me.