I don't believe for a single nanosecond that Gabby Giffords wrote that. I think her husband wrote it and she signed it.
I was watching her head nod during the defeat speech. It kept time with statements O'bama was making as he scolded the Senate, the NRA, and us gun owners in general. I can only assume that if she can nod her head when she hears something she likes, she can nod her head when she hears something she likes that someone wrote for her. I can't know for sure who wrote it, but I do believe she can follow along.