'Queen of Versailles' Family -- Victoria Siegel Was Cyberbullied Right Before Death

Victoria Siegel was the victim of vicious cyberbullying ... which her family believes pushed her over the edge and ultimately might have led to her death.

The Siegel family says the ex-girlfriend of Victoria's boyfriend (who we're told she met in rehab) had been sending "hateful text messages" to Victoria. They say the texts were coming from the BF's phone, and our sources say it was also happening on social media.

The family says Victoria got one of the bullying texts the morning of her death, and adds ... "While we cannot be sure, [the messages] may have affected her emotional state at a time when she was emotionally vulnerable."

We're told the family does not believe Victoria intended to kill herself ... because they were taking a family cruise this week, and Victoria rushed to get her passport in time for the trip. Instead, they're leaning toward an accidental overdose ... possibly triggered by the bullying.