Victoria Siegel, the daughter of billionaire resorts magnates Jackie and David Siegel, died due to an accidental drug overdose, according to an autopsy released Wednesday.

The 18-year-old's death was the result of "acute" methadone and sertraline toxicity, the Orange County Medical Examiner's Office concluded, The Hollywood Reporter has learned.

She was found unresponsive by a housekeeper at the Siegel's mansion on Green Cove Island In Windermere, Florida, and was later pronounced dead at a hospital, June 6.

The family's lawyer Michael Marder said in June that the teenager had previously undergone voluntary rehabilitation after realizing that she is being too dependent on prescribed medication (Xanax) which she took to help her with her seizures, Sky News reported.

Marder added that text messages she had received hours prior her death may have contributed to the tragedy.

Her boyfriend's ex-girlfriend, with whom he has a child, reportedly sent Victoria "cruel and hateful text messages" using the guy's phone.

"These messages were clearly intended to hurt Victoria and, while we cannot be sure, may have affected her emotional state at a time when she was emotionally vulnerable," explained Marder.

Meanwhile, the couple, who starred in their own 2012 show "Queen of Versailles," which documents their extravagant lifestyle including a plan to build the largest home in America, believe that their daughter did not die in vain.

To raise awareness about addiction, David and his wife Jacke, 49, created the Victoria's Voice Foundation.

"One hundred percent of my focus right now is on saving lives. Not on business, not on houses, not on reality shows," David told People. "I want my daughter's legacy to be that thousands of lives will be saved because she lost hers. That's what's keeping us sane. We could have crawled into bed, pulled the covers over our head and been a basket case, but instead we embarked on this journey to help other people, to save other families from going through what we've gone through."

"By doing this, it's given us some strength, knowing that we're going to save other lives and that Victoria didn't die in vain," Jackie said. "That maybe death has a greater purpose."