Last year, police recovered all the pieces of jewellery taken from her house, but, according a lawsuit filed by German insurance giant Allianz, Paris has still failed to return the items.
The suit states: "Despite having recovered Damiani's jewellery, [Hilton has] failed to return all of the jewellery to Damiani as required by the Agreements."
In 2007, Damiani loaned Paris $60,000 of jewellery to wear for public appearances and as part of the deal, she agreed to stash the valuables in a safe or a vault whenever she wasn't wearing it.
The suit claims she did none of that and often left her mansion's front door unlocked and its alarm system turned off.
It stated: "On Friday, December 18, 2009, in the early morning hours, Ms. Hilton left her mansion and attended a party at Bar Delux in Hollywood, California. At some point that night, the Damiani jewelery was placed in Ms. Hilton's closet and not in the safe as required by the Agreements.
"On December 18, 2009, Ms. Hilton left the front door to her mansion unlocked. Like the front door, Ms. Hilton also left the safe unlocked that was supposed to be used to secure the loaned Damiani jewelery."
According to the New York Daily News newspaper, the suit claims a man in a hooded sweatshirt then strolled in through the front door and took off with $2.8 million of jewellery that was "sitting in plain sight" in Paris' closet.
Paris' spokesperson refused to comment.