Siegel is the daughter of the billionaire couple featured in the 2012 documentary about the family's unfinished Orlando-area super-mansion.
"The Siegel family is devastated and heartbroken by the loss of their beloved Victoria, age 18," the family's attorney Michael Marder said in a statement to ABC News. "They are hurt, deeply wounded and they are grieving. Victoria was a beautiful spirit with a wonderful smile who was greatly loved, and will be deeply missed."
Marder said that the girl "had a history of seizures and was prescribed medication for this condition."
"Unfortunately she became dependent and struggled with this condition," he added. "She voluntarily underwent rehabilitation and was working hard to address this problem."
The Siegel family was at a wedding in Park City, Utah this past weekend and was planning to return to Orlando to begin a family cruise on the following Monday, the attorney added.
"While an autopsy has been performed the cause of death has not been determined," the statement said. "It is likely that Victoria ingested one or more drugs prior to her death, however, we cannot determine at this time whether or not the drugs she took were in fact prescribed medication, something else, or where and how these drugs may have been obtained."
The same statement was also posted to Jackie Siegel’s Facebook on late Monday. The toxicology report has yet to be released and the investigation into the death is ongoing.
Victoria was one of David and Jackie Siegel’s eight children. Jackie, known as the “Queen of Versailles” from the documentary chronicling her still-unfinished quest to build the biggest house in America, confirmed her daughter’s death on Sunday.
David Siegel is the founder and CEO of Westgate Properties, the biggest time share company in the world.