The 50-year-old sister of King Felipe told the court in Mallorca that she had never asked her husband, Inaki Urdangarin, how he ran a property company they jointly owned.
Inaki Urdangarin is accused of using his royal connections to generate business income they used for private spending.
Both deny any wrongdoing. Fifteen other defendants are also on trial.
Princess Cristina could face a maximum of eight years in jail if found guilty.
She denies knowledge of the alleged embezzlement scam that also involves her husband and 16 other defendants.
Asked by her lawyer during the 20-minute appearance why she never talked with her husband about what the company did, Infanta Cristina said they “weren’t issues that interested me”.
“At that time my children were very small and we were very busy. He was in charge of the family expenses. I didn’t get involved in that,” she added.
The case was launched in 2010 and has become highly symbolic of perceived corruption among Spain’s elites, including the royal family.
In 2015, King Felipe stripped his sister and her husband Inaki Urdangarin of their titles, the Duke and Duchess of Palma de Mallorca.
Princess Cristina now lives in Switzerland, but remains the sixth in line to the Spanish throne and is the first member of the royal family to go on trial.
Her lawyers argued that as public prosecutors had refused to press charges against her, the counts should be dismissed.
However, the three judges agreed to continue with the prosecution using the evidence filed by the anti-corruption group Manos Limpias (Clean Hands).
The charges relate to the real estate company Aizoon that Princess Cristina owned with Inaki Urdangarin, a former Olympic handball medalist.
Princess Cristina is accused of making personal use of Aizoon funds for paying for clothes and dance lessons for the couple’s children, as well as work on the couple’s Barcelona mansion, which reduced the company’s taxable profits.
Inaki Urdangarin is alleged to have used the non-profit Noos Institute sports foundation he ran as a vehicle to win falsely inflated contracts from regional government bodies, before channeling the money to personal accounts via tax havens.
Noos is alleged to have received more than €6m ($6.5 million) of public money, most of it from the Balearic Islands and Valencia regional governments.
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