The 47-year-old has not been named as a suspect in the corruption probe opened at the end of 2011 by a judge on the Mediterranean island of Mallorca.
But the graft allegations facing her husband have cast a growing shadow of suspicion over her role in the affair.
Urdangarin and his former partner Diego Torres are suspected of syphoning off money paid by regional governments to stage sports and tourism events to the non-profit Nóos Institute, which Urdangarin chaired from 2004 to 2006.
Both men have denied any wrongdoing and have not been charged with any crime.
Urdangarin, a former Olympic handball player, sought to distance his wife and the rest of the royal family from his business dealings when he was questioned in court last month by the judge leading the investigation.
But last week Torres provided the judge with emails that were leaked to the press which appear to show that Urdangarin regularly consulted his wife -- a member of the board of the Nóos Institute -- about the body's affairs.
Carlos Garcia Revenga, the longtime personal secretary to Princes Cristina and her older sister Princess Elena, was questioned by the judge last month after Torres submitted another batch of e-mails that suggested he was actively involved in the Nóos Institute's dealings.
Princess Cristina, who works as the director of social welfare programmes at Barcelona-based financial services group La Caixa's charitable foundation, has kept a low profile since the scandal broke.
The easy smile she was known for has been replaced by a serious expression during her the rare outings.
"The deterioration in Princess Cristina's image has no turning back, at least for a long time," Emilio de Diego, a history professor at Madrid's Complutense University, told AFP.
"Princess Cristina has always been the wayward daughter of the family, I think some of the monarch's mistakes when it comes to family matters began there, by tolerating that she work at a private firm like La Caixa and collect a salary without renouncing her status as a princess," he added.
The corruption case has also burst the public image of Urdangarin as the ideal son-in-law which he had enjoyed since married Princess Cristina in a lavish ceremony in Barcelona on October 4, 1997.
A fan of various sports, especially sailing, Princess Cristina -- the seventh in line to the Spanish throne -- met Urdangarin at the 1996 Olympics in Atlanta where he was competing with Spain's handball team, which won a bronze medal.
"She likes muscular men who are athletic, tall and sexy," said Andrew Morton, the author of a biography on Princess Diana who recently published a book on Princess Cristina and three other female members of Spain's royal family.
"She is enormously competitive and obstinate," he added.
In 2009 Princess Cristina and her husband, along with their four children, moved from Barcelona to Washington where Urdangarin took up a job as an executive director of the US subsidiary of Spanish telecoms giant Telefonica.
The couple, who were given the title of Duke and Duchess of Palma when they wed, were living in the United States when the allegations of corruption at the Noos Institute first broke in Spain.
"All we want to do is live a normal life and you won't let us," she said when approached by a reporter from Spanish television station Telecinco at a Washington supermarket in February 2012, just before her husband was questioned in court in Palma for the first time.
In August 2012 the couple and their four children returned to Barcelona, where they own a mansion in the exclusive Pedralbes area that reportedly cost around €6 million ($8.0 million).
"It is possible that Princess Cristina did not know anything about all of this, but the increase in his personal fortune, all of that could not be ignored by a spouse who is very close to her husband," said Pilar Eyre, who wrote a top-selling biography of the princess' mother, Queen Sofia.