PORTLAND, Ore. -- The estate of a Vancouver woman killed in a sex trafficking case is suing the hotel where she was killed, and the website the killer used to find her.

The body of 24-year-old Ashley Benson was found in the stairwell of the Doubletree Hotel Lloyd Center on December 26, 2014.

“She's our daughter, she's a sister, she's an awesome mother, she's our friend,” Ashley's stepmom, Jodie Benson, told KGW shortly after Ashley's death.

Jodie Benson said it wasn't until her death that they discovered Ashley had been living a secret life in which she was the victim of sex trafficking.

“We can't bring Ashley back . . . but there are other girls out there who are caught up in this,” said Benson. “I want them to get the help they need and not do this anymore.”

This month, the estate of Ashley Benson filed a lawsuit in Multnomah County Court against Hilton hotel group, the Doubletree Hotel's owners and Backpage.com, the website through which Ashley's killer, Tae Bum Yoon, found her.

The $3.6 million lawsuit claims Backpage and Doubletree knew or should have known that Ashley was the victim of sex trafficking, and that Yoon was engaged in illegal sex trafficking activity.

The suit also claims Backpage and the hotel benefited financially from Ashley's exploitation. Additionally, it claims Backpage's policies were not designed to keep sex ads off their site, but rather, help traffickers create ads for commercial sex while skirting the site's rules.

Hilton planned to train workers in 2011 to spot and report sex trafficking but failed to follow through, according to the lawsuit.

Yoon should have been noticed by hotel staff for paying in cash, checking in during late hours and using a non-Oregon ID while having no luggage.

In June, Yoon was convicted of first degree manslaughter. He's currently serving an 18-year prison sentence.

Backpage and Hilton Worldwide Holdings Inc. (parent company of Doubletree) have not responded to requests for comment from KGW.

LAWSUIT: Read the full text of the lawsuit here