Suzi Hileman told CBS News Correspondent Ben Tracy what happened Jan. 8 after shots rang out.
Complete Coverage: Tragedy in Tucson
"I remember lying on the ground holding Christina's hand and looking at her. And telling her to stay with me, and, 'I can't do this alone, sweetie, I love you, and stay here. Christina, Christina.'"
On "The Early Show," Tracy asked Suzi Hileman, "So you're laying there, and you're looking at each other. What -- are you even processing what happened? I mean what does go through your mind?"
Suzi Hileman said, "Oh, yeah. I knew something was up with Christina, because her face, and her hair, and everything was just perfect and beautiful. But she wasn't talking. And she wasn't moving."
Suzi Hileman learned Christina died from her husband, Bill.
Bill Hileman recalled, "Literally her first conscious act upon recognizing it was me in the room was to take my hand and look me in the eyes and ask, 'What about Christina?" There was only one way to deal with it, upon advice and 40 years of knowing her and that was to let her know squarely that Christina had passed, we lost her."
Suzi Hileman said, "We lost a friend two weeks ago. I had a girlfriend, and she's not around anymore. Everybody can relate to that."
"Early Show" co-anchor Jeff Glor noted the Hilemans say their relationship with Christina's parents is still very strong.
In Phoenix today, Jared Loughner is being arraigned on federal charges for that shooting rampage in Tucson two weeks ago. The U.S. Attorney filed a motion to move further proceedings to Tucson to reduce travel time for witnesses.
Six people were killed in that shooting and 13 wounded, including congresswoman Gabrielle Giffords. Giffords is at a Houston rehab center now where she remains in intensive care due to a buildup of brain fluid. Doctors say she is responding well to therapy, though.
Brain Fluid Keeps Giffords in Intensive Care