USOC spokesman Darryl Seibel said Barbara Bachman's condition has been upgraded from critical to serious but stable.
Mrs. Bachman was with her husband, Todd Bachman, both 62, when they were attacked by a Chinese man at an ancient monument in the heart of the Chinese capital on Saturday.
Todd Bachman was killed in the attack. The couple, from Lakeville, Minn., are parents of 2004 volleyball Olympian Elisabeth "Wiz" Bachman and in-laws of U.S. men's volleyball coach Hugh McCutcheon.
Elisabeth Bachman was with her parents at the time of the attack, but uninjured. Their Chinese tour guide was injured, but Beijing authorities have declined to release any details about her condition.
Shortly after the attack, which took place at midday, the assailant, Tang Yongming, 47, leapt to his death from a 130-foot high balcony on the Drum Tower, just five miles from the main Olympics site, the official Xinhua News Agency reported.
Dale Bachman, Todd's second cousin, told a news conference in Minneapolis that Todd Bachman, who was CEO of Twin Cities floral company Bachman's, Inc., was walking a few steps behind his wife and daughter at the Drum Tower when Barbara Bachman heard the commotion and turned to help her husband.
"That's when she was attacked," Dale Bachman said Saturday. "To me, that was a strong indication of her love. She is a fabulous person."
The assault came only hours after China's jubilant opening ceremony of the Summer Games and stunned the athletic community and embarrassed Chinese officials hosting President Bush.
Seibel said Monday that the Bachman family and the U.S. Olympics Committee members were "very, very, very happy to report her condition is upgraded." He said family members, including two daughters who flew in from their home in Minneapolis, were at the hospital with her.
"They're not at the point where they want to discuss the specific nature of the injuries," Seibel said of the Bachman family.
In an open letter released Monday by the U.S. Olympics Committee, Elisabeth and Hugh McCutcheon thanked friends, family, U.S. and Chinese officials and Olympic officials for their help during a "tremendously difficult time."
"We are extremely grateful for the outpouring of assistance and generosity that we have received and hope to convey our appreciation to everyone who has supported us and kept us in their thoughts and prayers," the letter said.
AP reporters at Peking Union Medical College Hospital, also called Beijing Xiehe Yiyuan, were not allowed onto the eighth floor of the facility, a section of the hospital that has been designated for the Olympics.
The committee said Sunday that Mrs. Bachman suffered multiple lacerations and stab wounds. She underwent eight hours of surgery and initially was in life-threatening, critical condition.
McCutcheon sat out the U.S. men's volleyball team's opening game against Venezuela on Sunday - a match that the Americans won 3-2 - to be with his wife at the hospital.
Police investigating the stabbing death have said the suspect was distraught over family problems. Chinese authorities unsettled by the attack during the Beijing Olympics tightened security at tourist spots around the city.
Wang Wei, vice president of the Beijing Olympic organizing committee, said Sunday that security in and around Olympic venues was already sufficient but would be increased at scenic spots in the capital.
He said Chinese investigators and U.S. Embassy officials believe Saturday's attack was "an isolated incident" and suggested such random acts are difficult to prevent. There was no indication the assailant knew his victims had any connection to the games, according to Olympic and Chinese authorities.
"Beijing is a safe city, but unfortunately we are not immune to violent acts," Wang told reporters.
Bush, in the Chinese capital to attend some Olympic events and meet with Chinese leaders, thanked President Hu Jintao on Sunday for his government's handling of the attack.
"Your government has been very attentive, very sympathetic, and I appreciate that a lot," Bush said.
Hu said his government took the incident "very seriously" and pledged to keep Washington apprised of the investigation.
Violent crime against foreigners is rare in tightly controlled China, and the assault occurred despite major security measures that have blanketed the capital city during the Olympics. A 100,000-strong security force plus countless volunteers have been deployed to protect against any trouble.
Police said Tang went through his second divorce in 2006 and grew increasingly despondent when his 21-year-old son started getting into trouble, Xinhua reported. The son was detained in May 2007 on suspicion of fraud, then received a suspended prison sentence in March this year for theft.