Pia Carusone said Wednesday on CBS's "The Early Show" that the Arizona congresswoman, who can carry on simple conversations, knows there was a traumatic event but has not been told about the severity of the wounds to others. That will happen in time when she's "at a higher level of communication," Carusone said.
"Doctors have said it's not really fair, as you can imagine, to tell someone something so tragic and someone that might not have the ability to ask the detailed questions that someone will have when they hear this news," she said.
Jared Loughner is charged in federal court with killing a federal judge and Giffords aide Gabriel Zimmerman and attempting to kill Giffords and two other staffers, Pamela Simon and Ron Barber.
Giffords was shot in the head and is undergoing intensive rehabilitation at TIRR Memorial Hermann in Houston.
Words in her vocabulary are returning and she is saying new words every day, Carusone said. Giffords can also sense when conversations turn serious and recognizes visitors, she said.
"Short phrases, simple thoughts. There's no doubt that she understands what's happening around her. She laughs at the appropriate times," Carusone said.
"She's just working really hard and progressing. It's paying off. And every day there's new progress that you see. So, you know, we feel very hopeful at her recovery."
Giffords' husband, astronaut Mark Kelly, has said he expects his wife to be well enough to be at Cape Canaveral, Fla., for his planned launch of the space shuttle Endeavour in April, although her doctor said it's too early to say.