Two of Giffords' congressional colleagues - Sen. Kirsten Gillibrand of New York and Rep. Debbie Wasserman Schultz of Florida - were also present in Giffords' hospital room when she opened her eyes. They described the moment to CBS' "The Early Show" Thursday.
(Scroll down to see video of Gillibrand and Wasserman Schultz, along with clips from Mr. Obama's speech.)
"We were talking about all the things we wanted to do as soon as she got better and all the things we hope to do with her. And we knew she was responding - she was holding our hands, and caressing our hands and squeezing them and moving her arms, moving her legs," Gillibrand recalled. "She started to open her eyes. And when her husband saw her making this effort, he urged her, said, 'Gabby, open your eyes, open your eyes.' And sure enough, she did."
Giffords' husband asked her to give a "thumbs up" if she could see the friends in the room.
"And a few moments later, she not only gave a thumbs up, she raised her whole arm. And it was just unbelievable and indescribable," Gillibrand said.
"This is a woman with the most remarkable determination," Wasserman Schultz said. "We were so excited when the doctors said, 'This is incredible progress.' [Giffords' neurosurgeon] Dr. Lemole outside the hospital room … he said, 'You know I don't really make much of emotion and friendship,' he said, 'but we saw the power of friendship in there.'"
Six people were killed and 14 were injured when a young man opened fire at a meet-and-greet event Giffords was holding at a busy Tucson, Ariz., supermarket.
Police say the man accused of the shootings, 22-year-old Jared Lee Loughner, shot Giffords as well as many in the line of people waiting to talk with her. The attack ended when bystanders tackled the man. He is in jail on federal charges as police continue to investigate.
Mr. Obama flew to Tucson Wednesday to meet with the injured and families of the slain and to try to soothe the nation in an address at the University of Arizona entitled "Together We Thrive: Tucson and America."
Gillibrand said that everyone present in Giffords' hospital room, but especially her husband Mark Kelly, were "just crying with joy" when Giffords opened her eyes.
"We know that she will overcome this. If anyone in the world can overcome an injury, of a severe nature, it's her," Gillibrand said. "Mark was telling us just a couple days ago how he was telling the doctors, she will be walking in a few weeks, you'll see."
"Shows you what a little bit of girl power can do," Wasserman Schultz said.